Production of isoflavone derivatives

ABSTRACT

Methods for the hydrogenation of isoflavones are described which provide access to workable quantities of isoflavan-4-ols, isoflav-3-enes, and isoflavans. The isoflavone derivatives can be obtained in high purity and in near quantitative yields whilst employing pharmaceutically acceptable reagents and solvents.

INTRODUCTION

The present invention relates to the hydrogenation of isoflavones andproducts thereof. The invention also relates to the synthesis ofphytoestrogenic isoflavone metabolites and derivatives from thehydrogenation products of isoflavones.

BACKGROUND OF THE INVENTION

Isoflavone metabolites possess a very wide range of important biologicalproperties including oestrogenic effects (WO 98/08503). Isoflavonemetabolites can be isolated from the urine of human volunteers subjectedto diets rich in plant isoflavanoids such as soya, lentils, peas andbeans.

In spite of the recently discovered biological significance ofisoflavone metabolites there is not at present a general method suitablefor the large scale synthesis of these metabolites. The few reportedsyntheses of these metabolites utilise either catalytic hydrogenation orhydrogen transfer reduction of the corresponding isoflavones. Thesereduction reactions are found to be non-selective, extremely difficultto control and lead to mixtures of different products.

The reduction of 5,7-dihydroxyisoflavylium salts have been reported togive mixtures of isoflav-2-enes, isoflav-3-enes and isoflavans. Theindividual compounds are difficult to separate and can be obtained onlyin low yields. Sodium borohydride reductions of isoflavones are known,see Ádám Major et al. Liebigs Ann. Chem. (1988) 555-558, however thereactions are low yielding, typically not clean and substituents on thebasic isoflavone ring structure require tedious protective groups notaffected by metal hydrides.

Chromatography is often required to separate the reaction products andonly low yields of isoflavanones, isoflavan-4-ols, isoflavenes andisoflavans are obtained. The chromatography required is tedious andoften impracticable for large scale reactions Furthermore, attempts toimprove the yield and purity of products obtained from hydrogenationreactions has been met with limited success as evidenced by publishedresults which are largely contradictory.

Solvents used in hydrogenation reactions of isoflavones reported in theliterature include N-methylpyrrolidinone, see Liepa, A. J., Aust. JChem., 1981, 34, 2647-55. However this solvent is unsuitable forpharmaceutical preparations of isoflavone metabolites and derivativesbecause N-methylpyrrolidinone is a severe eye irritant and a possiblecarcinogen. Furthermore the high boiling point of the solvent makes itextremely difficult to remove after the reduction.

Isoflavan-4-ols are key intermediates in the synthesis of isoflavenesand accordingly there is a need for more efficient and reliablesyntheses of isoflavan-4-ols, or at least comparable alternatives,acceptable than those known in the art. There is also a need forsynthetic methods for isoflavone hydrogenation which utilise solventspharmaceutically more acceptable than those previously reported.Therefore it is an object of the present invention to overcome or atleast alleviate one or more of the above-mentioned disadvantages of theprior art. It is an other object of the present invention to synthesisenovel isoflavone metabolites and derivatives.

Surprisingly hydrogenation conditions have been found by the presentinventors which enable the synthesis of isoflavone derivatives in goodto excellent yields. In particular the conditions found by the presentinventors allow for the hydrogenation of isoflavones to relatively puretetrahydroisoflavan-4-ol products in excellent yields, and without theneed for pharmaceutically unsuitable solvents and extensivechromatography in the hydrogenation reactions.

SUMMARY OF THE INVENTION

Thus the present invention provides a method for the hydrogenation of acompound of formula I

wherein

-   -   R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ are independently hydrogen,        hydroxy, OR₉, OC(O)R₉, OS(O)R₉, alkyl, haloalkyl, aryl,        arylalkyl, thio, alkylthio, amino, alkylamino, dialkylamino,        nitro or halo, and    -   R₉ is alkyl, haloalkyl, aryl, arylalkyl or alkylaryl,    -   to prepare a compound of formula II        wherein    -   R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈ and R₉ are as defined above.

The present invention also provides a method for the dehydration of acompound of formula II, which method may optionally include deprotectionor transformation steps, to prepare a compound of the formula III

wherein

-   -   R₁, R₂, R₃, R₄R₅, R₆R₇ and R₈ are independently hydrogen,        hydroxy, OR₉, OC(O)R₉, OS(O)R₉, alkyl, haloalkyl, aryl,        arylalkyl, thio, alkylthio, amino, alkylamino, dialkylamino,        nitro or halo, and    -   R₉ is alkyl, haloalkyl, aryl, arylalkyl or alkylaryl.

The present invention also provides a method for the hydrogenation of acompound of formula I to prepare a compound of formula IV

wherein

-   -   R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈ and R₉ are as defined above

The present invention also provides a method for the hydrogenation of acompound of formula III to prepare a compound of formula V

wherein

-   -   R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈ and R₉ are as defined above.

The present invention also provides compounds of formulae II, III, IVand V when prepared by a method described above and compositionscomprising same.

The present invention also provides novel compounds of the formulae I,II, III, IV and V and compositions comprising same.

DETAILED DESCRIPTION OF THE INVENTION

In the methods of the present invention, the starting isoflavone offormula I, the hydrogenation products isoflavan4-ol of formula II,isoflavan4-one of formula IV and isoflavan of formula V, and thedehydration product isoflav-3-ene of formula III preferably have thefollowing substituents wherein

-   -   R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ are independently hydrogen,        hydroxy, OR₉, OC(O)R₉, OS(O)R₉, alkyl, aryl, arylalkyl, thio,        alkylthio, bromo, chloro or fluoro, and R₉ is alkyl, fluoroalkyl        or arylalkyl;    -   more preferably they have the following substituents wherein    -   R₁ is hydroxy, OR₉ or OC(O)R₉,    -   R₂, R₃, R₄R₅, R₆ and R₇ are independently hydrogen, hydroxy,        OR₉, OC(O)R₉, alkyl, aryl or arylalkyl,    -   R₈ is hydrogen, and    -   R₉ is methyl, ethyl, propyl, isopropyl or trifluoromethyl; and    -   most preferably they have the following substituents wherein    -   R₁ is hydroxy, OR₉ or OC(O)R₉,    -   R₂, R₃, R₄, R₅ and R₇ are independently hydrogen, hydroxy, OR₉,        OC(O)R₉, alkyl, aryl or arylalkyl,    -   R₆ and R₈ are hydrogen, and    -   R₉ is methyl.

The particularly preferred compounds of formula I are4′,7-diacetoxyisoflavone (daidzein diacetate) and7-acetoxy4′-methoxyisoflavone;

-   -   the particularly preferred compounds of formula II are        4′,7-diacetoxyisoflavan-4-ol (tetrahydrodaidzein diacetate) and        7-acetoxy-4′-methoxyisoflavan4-ol;    -   the particularly preferred compounds of formula III are        4′,7-diacetoxyisoflav-3-ene (dehydroequol diacetate),        4′,7-dihydroxyisoflav-3-ene (dehydroequol),        7-acetoxy-4′-methoxyisoflav-3-ene and        7-hydroxy-4′-methoxyisoflav-3-ene;    -   the particularly preferred compounds of formula IV are        4′,7-diacetoxyisoflavan-4-one (diacetoxydihydrodaidzein) and        4′,7-dihydroxyisoflavan-4-one (dihydrodaicizein); and    -   the particularly preferred compounds of formula V are        4′,7-diacetoxyisoflavan (equol diacetate) and        4′,7-dihydroxyisoflavan (equol).

The novel compounds of the formulae I, II, III, IV and V preferably havethe following substituents wherein

-   -   R₁ is hydroxy, OR₉, OC(O)R₉, thio, alkylthio, or halo,    -   R₂, R₃, R₄, R₅, R₆, R₇ and R₈ are independently hydrogen,        hydroxy, OR₉, OC(O)R₉, OS(O)R₉, alkyl, aryl, thio, alkylthio or        halo, and    -   R₉ is alkyl, fluoroalkyl or arylalkyl    -   with the proviso that    -   at least one of R₅, R₆ and R₇ is not hydrogen, or    -   when R₅, R₄ and R₇ are all hydrogen, then R₃ is hydroxy, OR₉,        OC(O)R₉, OS(O)R₉, alkyl, aryl, thio, alkylthio or halo; and    -   more preferably they have the following substituents wherein    -   R₁ is hydroxy, OR₉ or OC(O)R₉,    -   R₂ and R₃ are independently hydrogen, hydroxy, OR₉ or OC(O)R₉,    -   R₄, R₅, R₆, and R₈ are hydrogen,    -   R₇ is hydroxy, OR₉, OC(O)R₉, alkyl, aryl or halo, and    -   R₉ is methyl, ethyl, propyl, isopropyl, trifluoromethyl or        benzyl; or    -   wherein    -   R₁ is hydroxy, OR₉, OC(O)R₉,    -   R₂ and R₃ are independently hydrogen, hydroxy, OR₉ or OC(O)R₉,    -   R₅ is OR₉, OC(O)R₉, alkyl, aryl or halo,    -   R₄, R₆, R₇, and R₈ are hydrogen, and    -   R₉ is methyl, ethyl, propyl, isopropyl, trifluoromethyl or        benzyl.

Most preferably the novel compounds of formulae I, II and III are:

-   -   4′,7,8-Triacetoxyisoflavone    -   7,8-Diacetoxy-4′-methoxyisoflavone    -   4′,7-Diacetoxy-8-methylisoflavone    -   3′,7-Diacetoxy-8-methylisoflavone    -   7-Acetoxy-4′-methoxy-8-methylisoflavone    -   4′,7-Diacetoxy-3′-methoxy-8-methylisoflavone    -   4′,5,7-Triacetoxyisoflavone    -   4′,7,8-Triacetoxyisoflavan4-ol    -   7,8-Diacetoxy-4-methoxyisoflavan-4-ol    -   4′,7-Diacetoxy-8-methylisoflavan-4-ol    -   3′,7-Diacetoxy-8-methylisoflavan4-ol    -   7-Acetoxy-4′-methoxy-8-methylisoflavan-4-ol    -   4′,7-Diacetoxy-3′-methoxy-8-methylisoflavan-4-ol    -   4′,5,7-Triacetoxyisoflavan-4-ol    -   4′,7,8-Trihydroxyisoflavan-4-ol    -   7,8-Dihydroxy-4-methoxyisoflavan-4-ol    -   4′,7-Dihydroxy-8-methylisoflavan-4-ol    -   3′,7-Dihydroxy-8-methylisoflavan-4-ol    -   7-Hydroxy-4′-methoxy-8-methylisoflavan-4-ol    -   4′,7-Dihydroxy-3′-methoxy-8-methylisoflavan-4-ol    -   4′,5,7-Trihydroxyisoflavan-4-ol    -   4′,7,8-Triacetoxydehydroequol (4′,7,8-Triacetoxyisoflav-3-ene)    -   7,8-Diacetoxy4-methoxydehydroequol        (7,8-Diacetoxy4-methoxyisoflav-3-ene)    -   4′,7-Diacetoxy-8-methylisoflav-3-ene    -   3′,7-Diacetoxy-8-methylisoflav-3-ene    -   7-Acetoxy4′-methoxy-8-methylisoflav-3 -ene    -   4′,7-Diacetoxy-3′-methoxy-8-methylisoflav-3-ene    -   4′,5,7-Triacetoxyisoflav-3-ene    -   Isoflav-3-ene-4′,7,8-triol    -   4′-Methoxyisoflav-3-ene-7,8-diol    -   8-Methylisoflav-3-ene-4′,7-diol    -   8-Methylisoflav-3-ene-3′,7-diol    -   4′-Methoxy-8-methylisoflav-3 -ene-7-ol    -   3′-Methoxy-8-methylisoflav-3-ene4′,7-diol    -   Isoflav-3-ene4′,5,7-triol    -   4′,7-Dihydroxy-8-methylisoflavan4-ol    -   7-Hydroxy-4′-methoxy-8-methylisoflavan-4-ol

The term “alkyl” is taken to mean both straight chain and branched chainalkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl,secbutyl, tertiary butyl, and the like. Preferably the alkyl group is alower alkyl of 1 to 6 carbon atoms. The alkyl group may optionally besubstituted by one or more of fluorine, chlorine, bromine, iodine,carboxyl, C₁-C₄-alkoxycarbonyl, C₁-C₄-alkylamino-carbonyl,di-(C₁-C₄-alkyl)-amino-carbonyl, hydroxyl, C₁-C₄-alkoxy, formyloxy,C₁-C₄-alkyl-carbonyloxy, C₁-C₄-alkylthio, C₃-C₆-cylcoalkyl or phenyl.

The term “aryl” is taken to include phenyl and naphthyl and may beoptionally substituted by one or more C₁-C₄-alkyl, hydroxy,C₁-C₄-alkoxy, carbonyl, C₁-C₄-alkoxycarbonyl , C₁-C₄-alkylcarbonyloxy orhalo.

The term “halo” is taken to mean one or more halogen radicals selectedfrom fluoro, chloro, bromo, iodo and mixtures thereof, preferably fluoroand chloro, more preferably fluoro. Reference to for example “haloalkyl”includes monohalogenated, dihalogenated and up to perhalogenated alkylgroups. Preferred perhalogenated groups are trifluoromethyl andpentafluoroethyl.

The compounds of the invention include all salts, such as acid additionsalts, anionic salts and zwitterionic salts, and in particular includepharmaceutically acceptable salts.

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word “comprise”, and variations such as“comprises” or “comprising”, will be understood to imply the inclusionof a stated integer or step or group of integers or steps but not theexclusion of any other integer or step or group of integers or steps.

The hydrogenation is ideally preformed with hydrogen in the presence ofa reduction catalyst and a solvent. The reaction is preferably conductedunder hydrogen at a pressure of 1-20 atmospheres, more preferably 1-5atmospheres. The reaction may be performed from 10 to 60° C. and istypically carried out at room temperature.

The reaction time may range from 12 hours to 96 hours or more and istypically about 55 hours or more. Generally better yields and cleanerreactions are achieved with longer reaction times. It will beappreciated that reaction conditions may be varied depending on theindividual nature of the compounds and the progress of the hydrogenationreaction.

The reduction catalysts may be selected from heterogeneous catalysts(whereby the catalyst is insoluble in the reaction medium) or homogenouscatalysts (whereby the catalyst is soluble in the reaction medium).Examples of heterogeneous reduction catalysts include Raney nickel,palladium black, palladium hydroxide on carbon, palladium on activatedcarbon (1% Pd to 30% Pd), palladium on alumina powder, palladium onvarious barium salts, sodium borohydride reduced nickel, platinum metal,platinum black, platinum on activated carbon (1% Pt to 10% Pt), platinumoxide, rhodium salts, ruthenium salts and their chiral salts and zincoxide. Preferably the catalyst is palladium on activated carbon (1% Pdto 10% Pd), more preferably about 5% palladium on carbon. Platinum oxide(Adam's catalyst) is also a very useful hydrogenation catalyst for themethods of the present invention to produce predominantly cis-isomers ofisoflavan4-ols.

Examples of homogeneous reduction catalysts include chlorotris(triphenylphosphine)rhodium, chloro(trisphenylphosphine)hydridoruthenium(II) and pentacyanocobaltate (II).

The solvents suitable for use in the present invention include but arenot limited to C₁-C₈ alcohols and polyols, alkyl acetates,tetrahydrofuran, ethers, dioxane and C₁-C₃ acids. Preferably the solventis a C₁-C₆ alcohol or C₁-C₆ alkyl acetate, more preferably methanol,ethanol or ethyl actate, as well as propanol, isopropanol, butanol,isobutanol, secbutanol, tertiary butanol, methyl formate, ethyl formateand methly acetate. Most preferably the solvent is absolute methanol,ethanol or ethyl acetate.

The present inventors have found that with a judicious choice ofcatalysts, solvents and optionally protecting groups, isoflavones arereduced cleanly and in high yields to corresponding isoflavanols. Inparticular the use of absolute methanol or ethanol as a solvent providedfor very clean catalytic hydrogenation over 5% palladium on charcoal ofisoflavones to afford up to quantitative yields of isoflavanols. Inmethods where, for example, 10% palladium on charcoal is employed, thereaction can proceed more rapidly, at times being complete within 12hours. The ratio of cis- and trans-isomers of the isoflavan-4-olhydrogenation product can vary with the choice of catalysts and thenature of the isoflavone substitute. By varying the methods of thepresent invention it is possible to influence the isomeric ratioachieved during the reduction process.

Of particular interest are isoflavones with oxygen substitution (orprecursors to oxygen substitution) at the 4′- and 7-positions asreduction of these compounds leads to the biologically importantdehydroequol or precursors thereof. A convenient starting material isdaidzein which is readily obtained by established routes.

It will be understood that some moieties on the isoflavone rings mayrequire protection or derivatisation prior to being subjected tohydrogenation. For example it may be desirable to protect free hydroxymoieties with groups such as an acetoxy group to assist in thesolubility of the substituted isoflavones and/or their susceptibility tohydrogenation. Protecting groups can be carried out be well establishedmethods known in the art, for example as described in Protective Groupsin Organic Synthesis, T. W. Greene.

In particular the present inventors have found it is useful to protecthydroxy groups when present as esters or ethers prior to reduction, withacetoxy or methoxy groups most favoured. Acylation is preferably carriedout with the hydroxy compounds in a solvent mixture of a carboxylic acidanhydride and base. Protecting free hydroxy groups prior tohydrogenation increases yields up to and including quantitative yields.The reaction products are generally cleaner and do not require achromatography step in the purification and isolation of thehydrogenation products.

Thus surprisingly, tetrahydrodaidzein diacetate was obtained inquantitative yield when the catalytic hydrogenation of diacetoxydaidzeinin ethanol was continued for 55 h. Spectroscopic analysis establishedthe product to be a 1:1 mixture of cis- and trans-isomers. Pleasingly,no further reduction of tetrahydrodaidzein was observed even if thereduction was continued for longer periods of time.

In a similar manner it was also surprisingly found that the protectedisoflavone 7-acetoxy-4′-methoxydaidzein smoothly and cleanly underwenthydrogenation in ethanol to afford a quantitative yield of a 1:1 mixtureof cis- and trans-isomers of 7-acetoxy-4′-methoxyisoflavan-4-ol. Thisreaction appears to be quite general and was repeated on many differentsubstrates in amounts of up to one half gram and more.

In this regard the inventors have found conditions which allow for thelarge scale generation of clean and near quantitative yields ofisoflavan-4-ols compounds by hydrogenation of corresponding isoflavones.In particular, it has been found that kilogram quantities of diacetoxydaidzein undergo smooth and efficient reduction to the isomeric cis- andtrans-4′,7-diacetoxyisoflavan-4-ols. The isomeric ratios can beinfluenced by the percentage of palladium in the catalyst.

The cis-/trans-isomeric mixtures are able to be dehydrated toisoflav-3-enes without the need for separation. However, is desired, themixtures are able to be separated by a variety of methods as set outbelow.

The mixture of cis- and trans-tetrahydrodaidzein compounds are able tobe separated by preparative HPLC. This mode of separation is quitetedious and limited to small amounts of material. Since reasonablequantities of the diacetoxy isoflavanols were able to be prepared,fractional crystallisation was attempted to separate the cis- andtrans-isomers. A single recrystallisation of the 1:1 mixture fromethanol gave predominantly trans-diacetoxytetrahydrodaidzein (50% yield:73% purity) (cis-isomer 27%). Subsequent recrystallisations from ethanolafforded the pure trans-isomer in 25% overall yield.

Likewise the 7-acetoxy-4′-methoxyisoflavan-4-ol was able to befractionally recrystallised to give the pure trans-isomer, with thefiltrate containing increased proportions of the cis-isomer.

Most hydrogenations yielded 1:1 mixtures of cis- andtrans-isoflavan-4-ols. However one derivative of note was7-hydroxy-4′-methoxy-8-methylisoflavone, the hydrogenation of whichafforded predominantly the trans-isomer in excellent yield.

Synthesis of tetrahydrodaidzein and related derivatives was achieved byremoval of the protecting acetoxy groups under mild conditions,preferably with imidazole in ethanol at reflux. Tetrahydrodaidzein wasisolated in 80% yield after crystallisation from aqueous ethanol.

Dehydration of isoflavan-4-ols leads to the unsaturated isoflav-3-enes.Thus reaction of a cis-/trans-mixture of isoflavan-4-ols with benzoylchloride/dimethylformamide at 100° C. has been reported in theliterature by Liepa to give the desired isoflav-3-ene dehydrationproduct. However this reaction could only be repeated in low yield.Dehydration may also be effected by treatment with acids such assulfuric acid, hydrochloric acid, polyphosphoric acid, thionyl chlorideand the like. Alternative methods of dehydration using p-toluenesulfonicacid or trifluoroacetic acid in refluxing dichloromethane were alsoinvestigated, but these methods also afforded the isoflavenes in lowyields.

Generally the present inventors found the dehydration reagent of choiceto be phosphorus pentoxide in dichloromethane, which can yieldisoflavenes in yields of greater than 60%. The dehydration reactions canbe carried out on the hydrogenation products directly, or deprotectedderivatives thereof.

Synthesis of dehydroequol was achieved by removal of the protectingacetoxy groups under mild conditions as described for the synthesis oftetrahydrodaidzein, and dehydroequol was purified by standardcrystallisation solvent mixtures such as ethanol/water. Otherisoflav-3-ene derivatives may be prepared by similar methods.

Hydrogen reduction of 4′,7-diacetoxydaidzein with Adam's catalyst(platinum(IV)oxide) in ethyl acetate under an atmosphere of hydrogenafforded 4′,7-diacetoxytetrahydrodaidzein. However unlike thepalladium-on-charcoal reduction in ethanol, reductions with Adam'scatalyst gave predominantly the cis-isomer of4′,7-diacetoxytetrahydrodaidzein.

In another embodiment of the invention, hydrogenation of 4′,7-diacetoxydaidzein with 5% palladium-on-charcoal in ethyl acetate as solvent underan atmosphere of hydrogen gave 4′,7-diacetoxydihydrodaidzein inexcellent yield (80%). These conditions provide access toisoflavan-4-ones from the corresponding isoflavones in good to excellentyields.

Access to isoflavan derivatives such as equol is possible byhydrogenation of isoflav-3-enes with, preferably, palladium-on-charcoalin an alkyl acetate solvent under an atmosphere of hydrogen. Excellentyields of 75% and more of the hydrogenated products are obtainable bythese methods. The products are clean and are readily recrystallised.

The surprising results obtained by the present inventors are in sharpcontrast to those reported in the literature for other attemptedhydrogenations of isoflavones. One such marked advantage is the use ofalkyl acetates or alcohol solvents such as absolute methanol or ethanolin the hydrogenation reactions. The isoflavanols prepared by the methodsof the present invention are typically very crystalline and can beisolated in good purity, and without the need for chromatography. Theisoflavanols can be converted to isoflav-3-enes by dehydration. Furtherdeprotection or derivatisation steps can be employed by those skilled inthe art to obtain natural isoflavan4-ones, isoflavans, isoflavenes,metabolites and novel derivatives thereof as required.

The invention is further described in and illustrated by the followingExamples. The Examples are not to be construed as limiting the inventionin any way.

EXAMPLES

Acetylation Reactions

Example 1 4′,7 Diacetoxydaidzein

Method A

A mixture of daidzein (1.0 g, 3.9 mmol), acetic anhydride (5 ml) andpyridine (5 ml) was left in the dark at room temperature for 24 h. Thereaction mixture was poured into water (100 ml), stirred for 2 h andthen extracted with dichloromethane (3×50 ml). The dichloromethane layerwas washed with water, dried over anhydrous sodium sulfate andevaporated. The white residue was crystallised from methanol to yielddaidzein diacetate as white prisms (1.1 g, 83%). ¹H NMR (CDCl₃): δ 2.32(s, 3H, OCOCH₃), 2.36 (s, 3H, OCOCH₃), 7.18 (d, 2H, J 9.2 Hz, ArH), 7.19(d, 1H, J 9.0 Hz, H6), 7.31 (d, 1H, J 20 Hz H8), 7.59 (d, 2H, J 9.2 Hz,ArH), 8.00 (s, 1H, H2), 8.33 (d, 2H, J 8.2 Hz, ArH).

Method B

A mixture of daidzein (2.0 g, 7.9 mmol), acetic anhydride (10 ml) andpyridine (2 ml) was heated on an oil bath at 105-110 C for 1 h. Aftercooling the mixture to room temperature, it was stirred for a further 30min during which time the diacetate crystallised from the solution. Theproduct was filtered, washed thoroughly with water and recrystallisedfrom methanol to yield daidzein diacetate as colourless prisms (2.4 g,90%).

Example 2 7-acetoxy-4′-methoxyisoflavone

A mixture of 7-hydroxy-4′-methoxyisoflavanone (2.0 g, 7.5 mmol), aceticanhydride (10 ml) and pyridine (2 ml) was heated on an oil bath at105-110 C for 1 hour. After cooling the mixture to room temperature, itwas poured into water (100 ml), stirred for 2 hours and then extractedwith dichloromethane (3×50 ml). The dichloromethane layer was washedwith water, dried over anhydrous sodium sulfate and evaporated. Thewhite residue was crystallised from methanol to yield7-acetoxy-4′-methoxyisoflavone as colourless prisms (2.1 g, 91%). ¹H NMR(CDCl₃): δ 2.36 (s, 3H, OCOCH₃), 3.84 (s, 3H, OCH₃), 6.98 (d, 2H, J 8.7Hz, ArH), 7.16 (dd, 1H, J 1.9 Hz 8.6 Hz, H6), 7.30 (d, 1H, J 1.9 Hz H8),7.50 (d, 2H, J 8.7 Hz, ArH), 8.00 (s, 1H, H2), 8.32 (d, 1H, J 8.6 Hz,HS).

Example 3 3′,7-Diacetoxyisoflavone

3′,7-Diacetoxydaidzein was prepared from 3′,7-dihydroxyisoflavone (0.98g, 3.9 mmol), acetic anhydride (6 ml) and pyridine (1.1 ml) as describedfor 4′,7-diacetoxydaidzein. Yield: (1.0 g, 77%) m.p. 152° C. 1H NMR(CDCl₃): δ 2.31 and 2.36 (each s, 3H, OCOCH₃), 7.14 (m, 1H, ArH), 7.18(dd, 1H, J 2.0 Hz 8.6 Hz, H6), 7.31 (d, 1H, J 2.0 Hz H8), 7.37-7.45 (m,3H, ArH), 8.03 (s, 1H, H2), 8.32 (d, 1H, J 8.6 Hz, H5). Mass spectrum:rm/z 338 (M, 8%); 296 (53); 254 (100); 253 (60).

Example 4 7-Acetoxy-3′-methoxyisoflavone

7-Acetoxy-3′-methoxyisoflavone was prepared from7-hydroxy-3′-methoxyisoflavone (1.7 g, 6.3 mmol), acetic anhydride (6ml) and pyridine (1.0 ml) as described for 4′,7-diacetoxydaidzein.Yield: (1.6 g, 81%) m.p. 118° C. 1H NMR (CDCl₃): δ 2.36 (s, 3H, OCOCH₃),3.85 (s, 3H, OMe), 6.95 (dd, 1H, J 2.0 Hz 8.3 Hz, H6), 6.70-7.40 (m, 5H,ArH), 8.01 (s, 1H, H2), 8.32 (d, 1H, J 8.7 Hz, H5).

Example 5 4′,7-Diacetoxy-3′-methoxyisoflavone

4′,7-Diacetoxy-3′-methoxyisoflavone was prepared from4′,7-dihydroxy-3′-methoxyisoflavone (0.37 g, 1.3 mmol), acetic anhydride(2.5 ml) and pyridine (0.4 ml) as described for 4′,7-diacetoxydaidzein.Yield: (0.36 g, 75%) m.p. 197° C. ¹H NMR (CDCl₃): δ 2.33, 2.36 (each s,3H, OCOCH₃), 3.88 (s, 3H, OMe), 7.06-7.17 (m, 2H, ArH), 7.19 (dd, 1H, J2.3 Hz 9.0 Hz, ArH), 7.32 (dd, 2H, J 2.3 Hz 7.6 Hz, ArH), 8.03 (s, 1H,H2), 8.32 (d, 1H, J 8.6 Hz, H5).

Example 6 7-Acetoxyisoflavone

7-Acetoxyisoflavone was prepared from 7-hydroxyisoflavone (2.6 g, 10.9mmol), acetic anhydride (16 ml) and pyridine (3.0 ml) as described for4′,7-diacetoxydaidzein. Yield: (2.5 g, 82%) m.p. 133° C. 1H NMR (CDCl₃):δ 2.36 (s, 3H, OCOCH₃), 7.18 (dd, 1H, J 2.2 Hz 8.6 Hz, H6), 7.31 (d, 1H,J 2.2 Hz H8), 7.39-7.57 (m, 5H, ArH), 8.00 (s, 1H, H2), 8.33 (d, 1H, J8.6 Hz, H5). Mass spectrum: m/z 280 (M, 28%); 237-(98); 238 (57).

Example 7 4′,7,8-Triacetoxyisoflavone

A mixture of 4′,7,8-trihydroxyisoflavone (1.4 g, 5.2 mmol), aceticanhydride (8.4 ml) and pyridine (2 ml) was heated on an oil bath at105-110° C. for 1 h. After cooling the mixture to room temperature, itwas stirred for a further 30 min during which time the diacetatecrystallised from the solution. The product was filtered, washedthoroughly with water and recrystallised from ethyl acetate to yield4′,7,8-triacetoxyisoflavone as colourless prisms (1.49 g, 73%) m.p.190-192° C. 1H NMR (CDCl₃): δ 2.32, 2.36, 2.42 (each s, 3H, OCOCH₃),7.18 (d, 2H, J 8.6 Hz, ArH), 7.28 (d, 1H, J 8.9 Hz, H6), 7.56 (d, 2H, J8.6 Hz H8), 7.98 (s, 1H, ArH), 8.18 (d, 1H, J 8.9 Hz, H5).

Example 8 7,8-Diacetoxy-4′-methoxyisoflavone

7,8-Diacetoxy-4′-methoxyisoflavone was prepared from7,8-dihydroxy-4′-methoxyisoflavone (0.82 g, 2.9 mmol), acetic anhydride(4.9 ml) and pyridine (0.9 ml) as described for4′,7,8-triacetoxyisoflavone. Yield: (0.9 g, 85%) m.p. 165° C. 1H NMR(CDCl₃): δ 2.36, 2.42 (each s, 3H, OCOCH₃), 3.84 (s, 3H, OCH₃), 6.98 (d,2H, J 9.0 Hz, ArH), 7.25 (d, 1H, J 8.7 Hz, H6), 7.48 (d, 2H, J 9.0 HzH8), 7.95 (s, 1H, H2), 8.20 (d, 1H, J 9.1 Hz, H5). Mass spectrum: m/z368 (M, 20%); 326 (15); 312 (18); 284 (80).

Example 9 4′,7-Diacetoxy-methylisoflavone

A mixture of 4′,7-dihydroxy-8-methylisoflavone (2.9 g, 10.8 mmol),acetic anhydride (18 ml) and pyridine (3 ml) was heated on an oil bathat 105-110° C. for 1 h. After cooling the mixture to room temperature,it was stirred for a further 30 min during which time the diacetatecrystallised from the solution. The product was filtered, washedthoroughly with water and recrystallised from ethyl acetate to yield4′,7-diacetoxy-8-methylisoflavone as colourless prisms (3.2 g, 84%). 1HNMR (CDCl₃): δ 2.31 (s, 3H, CH₃), 2.32, 2.39 (each s, 3H, OCOCH₃), 7.13(d, 1H, J 9.0 Hz, H6), 7.17 (d, 2H, J 8.7 Hz, ArH), 7.59 (d, 2H, J 8.7Hz, ArH), 8.07 (s, 1H, H2), 8.19 (d, 1H, J 8.7 Hz, H5).

Example 10 3′,7-Diacetoxy-8-methylisoflavone

3′,7-Diacetoxy-8-methylisoflavone was prepared from3′,7-dihydroxy-8-methylisoflavone (1.3 g, 4.8 mmol), acetic anhydride (8ml) and pyridine (1.5 ml) as described for4′,7-diacetoxy-8-methylisoflavone. Yield: (1.2 g, 70%) m.p. 112° C. ¹HNMR (CDCl₃): δ 2.31 (s, 3H, CH₃), 2.32, 2.39 (each s, 3H, OCOCH₃), 7.13(m, 2H, ArH), 7.37-7.45 (m, 3H, ArH), 8.1 (s, 1H, H2), 8.18 (d, 1H, J8.7 Hz, H5). Mass spectrum: m/z 352 (M, 6%); 310 (35); 268 (100); 267(60).

Example 11 7-Acetoxy-4′-methoxy-8-methylisoflavone

7-Acetoxy4′-methoxy-8-methylisoflavone was prepared from7-hydroxy4′-methoxy-8-methylisoflavanone (3.0 g, 10.6 mmol), aceticanhydride (10 ml) and pyridine (2.0 ml) as described for4′,7-diacetoxy-8-methylisoflavone. Yield: (2.0 g, 58%) m.p. 190-192° C.1H NMR (CDCl₃): δ 2.31 (s, 3H, CH₃), 2.38 (s, 3H, OCOCH₃), 3.84 (s, 3H,OMe), 6.98 (d, 2H, J 8.7 Hz, ArH), 7.12 (d, 1H, J 8.6 Hz, H6), 7.52 (d,2H, J 8.7 Hz, ArH), 8.03 (s, 1H, H2), 8.18 (d, 1H, J 8.6 Hz, H5). Massspectrum: 325 (M+1, 13%); 324 (M, 58%); 282 (100); 281 (42).

Example 12 4′,7-Diacetoxy-3′-methoxy-8-methylisoflavone

4′,7-Diacetoxy-3′-methoxy-8-methylisoflavone was prepared from4′,7-dihydroxy-3′-methoxy-8-methylisoflavone (0.42 g, 1.4 mmol), aceticanhydride (2.6 ml) and pyridine (0.5 ml) as described for4′,7-diacetoxy-8-methylisoflavone. Yield: (0.4 g, 74%) m.p. 209° C. 1HNMR (CDCl₃): δ 2.22 (s, 3H, CH₃), 2.32, 2.39 (each s, 3H, OCOCH₃), 3.89(s, 3H, OMe), 7.07-7.11 (m, 2H, ArH), 7.13 (d, 1H, J 8.6 Hz, H6), 7.32(d, 1H, J 1.5 Hz, ArH), 8.09 (s, 1H, H2), 8.18 (d, 1H, J 8.7 Hz, H5).

Hydrogenation Reactions:—Isoflavone→Isoflavan4ol

Example 13 4′,7-diacetoxytetrahydrodaidzein (4′7-Diacetoxyisoflavan4-ol)

Method A

Palladium-on-charcoal (5%, 0.08 g) was added to a suspension of4′,7-diacetoxydaidzein (0.5 g, 1.5 mmol) in absolute ethanol (400 ml)and the mixture was stirred at room temperature under a hydrogenatmosphere for 55 hours. The catalyst was removed by filtration throughCelite and the filtrate was evaporated in vacuo to yield4′,7-diacetoxytetrahydrodaidzein (0.51 g, 100%) in quantitative yield. Anuclear magnetic resonance spectrum revealed the product to be a clean1:1 mixture of cis- and trans-4′,7-diacetoxytetrahydrodaidzein.

The cis- and trans-isomers were able to be separated by fractionalrecrystallisation. A 1:1 mixture of cis- andtrans-4′,7-diacetoxytetrahydrodaidzein (0.17 g), prepared as above, wasdissolved in excess absolute ethanol and concentrated on a rotaryevaporator. At the first sign of crystallisation, further concentrationof ethanol was stopped and the flask was cooled in an ice-bath. Theresulting crystals were filtered and washed with a small amount of coldabsolute ethanol. A nuclear magnetic resonance spectrum of the product(0.08 g) revealed it to be a mixturetrans4′,7-diacetoxytetrahydrodaidzein (73%) andcis-4′,7-diacetoxytetrahydrodaidzein (27%). Further recrystallisationsof the mixture from ethanol yielded the puretrans-4′,7-diacetoxytetrahydrodaidzein (0.04 g, 24%).

The filtrate yielded predominantly cis-isomer. Nuclear magneticresonance spectroscopic analysis revealed the substance to be a mixtureof cis4′,7-diacetoxytetrahydrodaidzein (73%) andtrans4′,7-diacetoxytetrahydrodaidzein (27%).

For trans4′,7-Diacetoxyisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.28 (s, 3H,OCOCH₃), 2.29 (s, 3H OCOCH₃), 3.14 (ddd, 1H, J 3.7 Hz, 7.9 Hz, 9.1 Hz,H3), 4.24 (dd, 1H, J 9.1 Hz, 11.3 Hz, H2); 4.35 (dd, 1H, J 3.7 Hz, 11.3Hz, H2), 4.87 (d, 1H, J 7.9 Hz, H4), 6.61 (d, 1H, J 2.3 Hz, H8), 6.70(dd, 1H, J 2.3 Hz, 8.4 Hz, H6), 7.06 (d, 2H, J 8.6 Hz, ArH), 7.23 (d,2H, J 8.4 Hz, ArH), 7.44 (dd, 1H, J 0.8 Hz, 8.4 Hz, H5). ¹³C NMR(CDCl₃): 20.98 (OCOCH₃), 46.18 (C3), 68.04 (C2), 69.01 (C4), 109.67(C8), 114.26 (C6), 121.96, 128.96 (ArCH), 129.40 (C5).

For cis-4′,7-Diacetoxyisoflavan-4-ol: ¹H NMR (CDCl₃): δ 2.28 (s, 3H,OCOCH₃), 2.29 (s, 3H, OCOCH₃), 3.30 (dt, 1H, J 3.4 Hz, J 11.8 Hz, H3),4.31 (ddd, 1H, J 1.4 Hz, 3.6 Hz, 10.5 Hz, H2); 4.56 (dd, 1H, J 10.5 Hz,11.8 Hz, H2), 4.75 (dd, 1H, J 1.3 Hz, 3.2 Hz, H4). 6.66 (dd, 1H, J 2.3Hz, 8.7 Hz, H6), 6.69 (d, 1H, J 2.3 Hz, H8), 7.08 (d, 2H, J 8.6 Hz,ArH), 7.26 (d, 1H, 8.4 Hz, H5), 7.29 (d, 2H, J 8.6 Hz ArH). ¹³C NMR(CDCl₃); 20.98 (OCOCH₃), 43.52 (C3), 64.10 (C2), 66.46 (C4), 110.08(C6), 114.09 (C8), 121.82, 129.40 (ArCH), 131.10 (C5).

Method B

Palladium-on-charcoal (5%, 3.1 g) was added to a suspension of4′,7-diacetoxydaidzein (30.0 g) in absolute methanol (3600 ml) and themixture was stirred at room temperature under a hydrogen atmosphere for55 hours. The catalyst was removed by filtration through Celite and thefiltrate was evaporated in vacuo to yield4′,7-diacetoxytetrahydrodaidzein (29.5 g, 96%). A nuclear magneticresonance spectrum revealed the product to be a clean 2:1 mixture ofcis- and trans-4′,7-diacetoxytetrahydrodaidzein.

Method C

Palladium-on-charcoal (10%, 3.0 g) was added to a suspension of4′,7-diacetoxydaidzein (30.1 g) in absolute methanol (3600 ml) and themixture was stirred at room temperature under a hydrogen atmosphere for15 hours. The catalyst was removed by filtration through Celite and thefiltrate was evaporated in vacuo to yield4′,7-diacetoxytetrahydrodaidzein (28.5 g, 94%). A nuclear magneticresonance spectrum revealed the product to be a clean 1:1 mixture ofcis- and trans4′,7-diacetoxytetrahydrodaidzein.

Method D

Palladium-on-charcoal (5%, 100 g) was added to a suspension of4′,7-diacetoxydaidzein (980 g) in absolute methanol (100 L) and themixture was stirred at room temperature under a hydrogen atmosphere for78 hours. The catalyst was removed by filtration through a ceramiccandle filtratation apparatus and the filtrate was evaporated in vacuoto yield 4′,7-diacetoxytetrahydrodaidzein (820 g, 83%). A nuclearmagnetic resonance spectrum revealed the product to be a clean 2:1mixture of cis- and trans-4′,7-diacetoxytetrahydrodaidzein.

Example 14 Synthesis of 7-Acetoxy-4′-methoxyisoflavan-4-ol

Palladium-on-charcoal (5%, 0.08 g) was added to a suspension of7-acetoxy-4′-methoxyisoflavone (0.5 g, 1.6 mmol) in absolute ethanol(400 ml) and the mixture was stirred at room temperature under ahydrogen atmosphere for 55 hours. The catalyst was removed by filtrationthrough Celite and the filtrate was evaporated in vacuo to yield7-acetoxy-4′-methoxyisoflavan-4-ol (0.51 g, 100%) in quantitative yield.A nuclear magnetic resonance spectrum revealed the product to be a clean1:1 mixture of cis- and trans-7-acetoxy-4′-methoxyisoflavan-4-ol.

The cis- and trans-isomers were able to be separated by fractionalrecrystallisation. A 1:1 mixture of cis- andtrans-4′,7-diacetoxytetrahydrodaidzein, prepared as above, wasrecrystallised three times from ethanol to yield puretrans-7-acetoxy-4′-methoxyisoflavan4-ol. The filtrate yieldedpredominantly cis-isomer.

For trans-7-Acetoxy-4′-methoxyisoflavan-4-ol; 1H NMR (CDCl ₃): 8 2.31(s, 3H, OCOCH₃), 3.14 (dt, 1H, J 3.8 Hz, 8.6 Hz, H3), 3.82 (s, 3H,OCH₃), 4.25 (dd, 1H, J 9.4 Hz, 11.3 Hz, H2); 4.37 (dd, 1H, J 4.1 Hz,11.3 Hz, H2), 4.93 (d, 1H, J 7.8 Hz, H4), 6.63 (d, 1H, J 2.3 Hz, H8),6.73 (dd, 1H, J 2.3 Hz, 8.3 Hz, H6), 6.93 (d, 2H, J 8.7 Hz, ArH), 7.19(d, 2H, J 8.7 Hz, ArH), 7.51 (d, 1H, J 7.9 Hz, H5).

For cis-7-Acetoxy4′-methoxyisoflavan-4-ol; 1H NMR (CDCl₃): 8 2.30 (s,3H, OCOCH₃), 3.28 (dt, 1H, J 3.4 Hz, J 12.1 Hz, H3), 3.84 (s, 3H, OCH3),4.36 (ddd, 1H, J 1.4 Hz, 3.8 Hz, 10.1 Hz, H2); 4.57 (dd, 1H, J 10.1 Hz,11.3 Hz, H2), 4.75 (bs, 1H, H4), 6.58 (d, 1H, J 2.3 Hz, H8), 6.75 (dd,1H, J 2.3 Hz, 8.3 Hz, H6), 6.96 (d, 2H, J 8.6 Hz, ArH), 7.25 (d, 2H, 8.6Hz, ArH), 7.34 (d, 1H, J 8.3 Hz, H5).

Example 15 3′-7-Diacetoxyisoflavan4-ol

Palladium-on-charcoal (5%, 0.03 g) was added to a suspension of3′,7-diacetoxyisoflavanone (0.2 g, 0.6 mmol) in methanol (50 ml) and themixture was stirred at room temperature under a hydrogen atmosphere for55 h. The catalyst was removed by filtration through Celite and thefiltrate was evaporated in vacuo to yield 3′-7-diacetoxyisoflavan-4-olin quantitative yield. A nuclear magnetic resonance spectrum revealedthe product to be a clean 1:1 mixture of cis- andtrans-3′-7-diacetoxyisoflavan-4-ol.

For trans-3′-7-diacetoxyisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.31 and 2.32(each s, 3H, OCOCH₃), 3.17 (ddd, 1H, J 3.6 Hz, 8.6 Hz, 11.2 Hz, H3),4.26 (dd, 1H, J 9.2 Hz, 11.6 Hz, H2); 4.33 (m, 1H, H2), 4.91 (d, 1H, J7.9 Hz, H4), 6.60-6.73 (m, ArH), 6.97-7.16 (m, ArH), 7.25-7.48 (m, ArH).

For cis-3′-7-diacetoxyisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.30 and 2.31(each s, 3H, OCOCH₃), 3.31 (dt, 1H, J 3.3 Hz, J 11.6 Hz, H3), 4.31 (m,1H, H2); 4.57 (dd, 1H, J 10.6 Hz, 11.9 Hz, H2), 4.79 (bs, 1H, H4),6.60-6.73 (m, ArH), 6.97-7.16 (m, ArH), 7.25-7.48 (m, ArH).

Example 16 7-Acetoxy-3′-methoxyisoflavan-4-ol

Cis- and trans-7-acetoxy-3′-methoxyisoflavan-4-ol was prepared from7-acetoxy-3′-methoxyisoflavone (0.5 g, 1.6 mmol) andpalladium-on-charcoal (5%, 0.12 g) in methanol (100 ml) by the methoddescribed above.

For trans-7-acetoxy-3′-methoxyisoflavan4-ol; ¹H NMR (CDCl₃): δ 2.28 (s,3H, OCOCH₃), 3.15 (ddd, 1H, J 3.8 Hz, 8.3 Hz, 12.0 Hz, H3), 3.80 (s, 3H,OMe), 4.26 (dd, 1H, J 9.4 Hz, 11.3 Hz, H2); 4.32 (m, 1H, H2), 4.95 (d,1H, J 7.9 Hz, H4), 6.60-6.93 (m, ArH), 7.23-7.33 (m, ArH), 7.49 (d, J8.7 Hz, ArH).

For cis-7-acetoxy-3′-methoxyisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.28 (s,3H, OCOCH₃), 3.30 (dt, 1H, J 3.3 Hz, J 11.7 Hz, H3), 4.31 (m, 1H, H2);4.58 (dd, 1H, J 10.5 Hz, 11.7 Hz, H2), 4.81 (bs, 1H, H4), 6.60-6.93 (m,ArH), 7.23-7.33 (m, ArH), 7.49 (d, J 8.7 Hz, ArH).

Example 17 4′,7-Diacetoxy-3′-methoxyisoflavan-4ol

Cis- and trans-4′-7-diacetoxy-3′-methoxyisoflavan-4-ol was prepared from4′-7-diacetoxy-3′-methoxyisoflavone (0.25 g, 0.7 mmol) andpalladium-on-charcoal (5%, 0.06 g) in methanol (50 ml) by the methoddescribed above.

For trans-4′-7-diacetoxy-3′-methoxyisoflavan-4-ol; ¹H NMR (CDCl ₃): 82.29, 2.31 (each s, 3H, OCOCH₃), 3.17 (ddd, 1H, J 3.8 Hz, 8.7 Hz, 12.5Hz, H3), 3.79 (s, 3H, OMe), 4.26 (dd, 1H, J 9.4 Hz, 11.3 Hz, H2); 4.32(m, 1H, H2), 4.93 (d, 1H, J 7.9 Hz, H4), 6.62-6.73 (m, ArH), 6.81-6.91(m, ArH), 6.99-7.05 (m, ArH), 7.30 (d, J 8.3 Hz, ArH), 7.48 (d, J 9.0Hz, ArH).

For cis-7-acetoxy-3′-methoxyisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.31,2.32(each s, 3H, OCOCH₃), 3.33 (dt, 1H, J 3.3 Hz, J 11.3 Hz, H3), 3.83 (s,3H, OMe), 4.31 (m, 1H, H2); 4.58 (t, 1H, J 10.5 Hz, H2), 4.82 (bs, 1H,H4), 6.62-6.73 (m, ArH), 6.81-6.91 (m, ArH), 6.99-7.05 (m, ArH), 7.30(d, J 8.3 Hz, ArH), 7.48 (d, J 9.0 Hz, ArH).

Example 18 7-Acetoxyisoflavan4-ol

Cis- and trans-7-acetoxyisoflavan-4-ol was prepared from7-acetoxyisoflavone (0.4 g, 1.4 mmol) and palladium-on-charcoal (5%,0.09 g) in absolute methanol (60 ml). m.p. 90° C. Mass spectrum: m/z 284(M, 10%); 226 (42); 138 (100); 137 (58).

For trans-7-acetoxyisoflavan4-ol; ¹H NMR (CDCl₃): δ 2.29 (s, 3H,OCOCH₃), 3.17 (m, 1H, H3), 4.27 (t, 1H, J 10.6 Hz, H2); 4.30 (m, 1H,H2), 4.97 (d, 1H, J 8.3 Hz, H4). 6.60-6.73 (m, ArH), 7.08 (d, J 8.7 Hz,ArH), 7.23-7.37 (m, ArH), 7.49 (d, J 8.7 Hz, ArH).

For cis-7-acetoxyisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.30 (s, 3H, OCOCH₃),3.33 (dt, 1H, J 3.4 Hz, J 11.7 Hz, H3), 4.36 (m, 1H, H2); 4.62 (t, 1H, J10.5 Hz, H2), 4.80 (bs, 1H, H4), 6.60-6.73 (m, ArH), 7.08 (d, J 8.7 Hz,ArH), 7.23-7.37 (m, ArH), 7.49 (d, J 8.7 Hz, ArH).

Example 19 4′,7,8-Triacetoxyisoflavan-4-ol

Palladium-on-charcoal (5%, 0.07 g) was added to a suspension of4′,7,8-triacetoxyisoflavone (0.5 g, 1.3 mmol) in methanol (100 ml) andthe mixture was stirred at room temperature under a hydrogen atmospherefor 55 h. The catalyst was removed by filtration through Celite and thefiltrate was evaporated in vacuo to yield4′,7,8-triacetoxyisoflavan-4-ol in quantitative yield. A nuclearmagnetic resonance spectrum revealed the product to be a clean 1:1mixture of cis- and trans-4′,7,8-triacetoxyisoflavan-4-ol. Massspectrum: m/z 400 (M, 5%); 358 (12); 298 (12); 256 (24); 196 (20); 162(70); 154 (100); 120 (80).

For trans4′,7,8-triacetoxyisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.28, 2.29.2.31 (each s, 3H, OCOCH₃), 3.20 (m, 1H, H3), 4.27 (dd, 1H, H2); 4.37 (m,1H, H2), 4.93 (d, 1H, J 7.9 Hz, H4), 6.78 (d, 1H, J 8.3 Hz, H8), 7.09(m, ArH), 7.11-7.31 (m, ArH), 7.39 (d, 1H, 1H, J 8.7 Hz, ArH).

For cis-4′,7,8-triacetoxyisoflavan4-ol; ¹H NMR (CDCl₃): δ 2.30, 2.31,2.32 (each s, 3H, OCOCH₃), 3.35 (m, 1H, H3), 4.38 (m, 1H, H2); 4.57 (t,1H, J 10.6 Hz, H2), 4.75 (bs, 1H, H4), 6.78 (d, 1H, J 8.3 Hz, H8), 7.09(m, ArH), 7.11-7.31 (m, ArH), 7.39 (d, 1H, J 8.7 Hz, ArH).

Example 20 7,8-Diacetoxy4-methoxyisoflavan-4-ol

7,8-Diacetoxy4-methoxyisoflavan4-ol was prepared from7,8-dihydroxy-4′-methoxyisoflavone (0.4 g, 1.1 mmol) in methanol (120ml) using palladium-on-charcoal (5%, 0.08 g) by the method describedabove.

For trans-7,8-diacetoxy-4-methoxyisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.29,2.30 (each s, 3H, OCOCH₃), 3.14 (ddd, 1H, J 3.9 Hz, 9.2 Hz, 12.5 Hz,H3), 3.79 (s, 3H, OCH₃), 4.24 (dd, 1H, J 9.6 Hz, 11.2 Hz, H2); 4.35 (m,1H, H2), 4.92 (d, 1H, J 7.8Hz, H4), 6.78 (d, 1H, J 8.6 Hz, H6), 6.90 (m,ArH), 7.13-7.22 (m, ArH), 7.38 (d, J 8.6 Hz, ArH).

For cis-7,8-diacetoxy-4-methoxyisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.30,2.31 (each s, 3H, OCOCH₃), 3.29 (dt, 1H, J 3.0 Hz, J 12.0 Hz, H3), 3.80(s, 3H, OCH₃), 4.36 (m, 1H, H2); 4.57 (t, 1H, J 10.6 Hz, H2), 4.75 (bs,1H, H4), 6.77 (d, 1H, J 8.6 Hz, H6), 6.90 (m, ArH), 7.13-7.22 (m, ArH),7.38 (d, J 8.6 Hz, ArH).

Example 21 4′,7-Diacetoxy-8-methylisoflavan4-ol

Palladium-on-charcoal (5%, 0.12 g) was added to a suspension of4′,7-diacetoxy-8-methylisoflavone (1.0 g, 2.8 mmol) in methanol (200 ml)and the mixture was stirred at room temperature under a hydrogenatmosphere for 55 h. The catalyst was removed by filtration throughCelite and the filtrate was evaporated in vacuo to yield4′,7-diacetoxy-8-methylisoflavan-4-ol in quantitative yield, m.p.135-37° C. A nuclear magnetic resonance spectrum revealed the product tobe a clean 1:1 mixture of cis- andtrans4′,7-diacetoxy-8-methylisoflavan4-ol. Mass spectrum: 356 (M, 53%);254 (86); 253 (100); 240 (80); 196 (37).

For trans-4′,7-diacetoxy-8-methylisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.02(s, 3H, CH₃), 2.30, 2.31 (each s, 3H, OCOCH₃), 3.15 (ddd, 1H, J 3.8 Hz,8.6 Hz, 11.7, H3), 4.27 (dd, 1H, J 9.4 Hz, 11.3 Hz, H2); 4.39 (m, 1H,H2), 4.92 (d, 1H, J 7.5 Hz, H4), 6.64 (d, 1H, J 8.0 Hz, H6), 7.06-7.32(m, ArH).

For cis-4′,7-diacetoxy-8-methylisoflavan4-ol; ¹H NMR (CDCl₃): δ 2.02 (s,3H, CH₃), 2.31, 2.32 (each s, 3H, OCOCH₃), 3.28 (dt, 1H, J 3.4 Hz, J11.7 Hz, H3), 4.40 (m, 1H, H2); 4.58 (dd, 1H, J 10.1 Hz, 11.7 Hz, H2),4.78 (bs, 1H, H4), 6.67 (d, 1H, J 8.0 Hz, H6), 7.06-7.32 (m, ArH).

Example 22 3′,7-Diacetoxy-8-methylisoflavan4-ol

3′,7-Diacetoxy-8-methylisoflavan-4-ol was prepared from3′,7-diacetoxy-8-methylisoflavone (0.25 g, 0.7 mmol) in methanol (50 ml)using palladium-on-charcoal (5%, 0.06 g) by the method described above.

For trans-3′,7-diacetoxy-8-methylisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.03(s, 3H, CH₃), 2.30, 2.32 (each s, 3H, OCOCH₃), 3.18 (ddd, 1H, J 3.8 Hz,8.3 Hz, 12.1 Hz, H3), 4.28 (dd, 1H, J 9.0 Hz, 10.9 Hz, H2); 4.39 (m, 1H,H2), 4.94 (d, 1H, J 8.7 Hz, H4), 6.65 (d, 1H, J 7.9 Hz, H6), 6.98-7.39(m, ArH).

For cis-3′,7-diacetoxy-8-methylisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.05(s, 3H, CH₃), 2.30, 2.32 (each s, 3H, OCOCH₃), 3.32 (dt, 1H, J 3.4 Hz, J12.0 Hz, H3), 4.39 (m, 1H, H2); 4.59 (dd, 1H, J 10.5 Hz, 11.7 Hz, H2),4.80 (bs, 1H, H4), 6.68 (d, 1H, J 8.3 Hz, H6), 6.98-7.39 (m, ArH).

Example 23 7-Acetoxy-4′-methoxy-8-methylisoflavan-4-ol

7-Acetoxy-4′-methoxy-8-methylisoflavan-4-ol was prepared from7-hydroxy-4′-methoxy-8-methylisoflavone (0.25 g, 0.8 mmol) in methanol(50 ml) using palladium-on-charcoal (5%, 0.08 g) by the method describedabove. This hydrogenation reaction predominantly yielded thetrans-isomer.

For trans-7-Acetoxy4′-methoxy-8-methylisoflavan4-ol; ¹H NMR (CDCl₃): δ2.02 (s, 3H, CH₃), 2.32 (s, 3H, OCOCH₃), 3.11 (ddd, 1H, J 3.8 Hz, 9.4Hz, 12.1 Hz, H3), 3.80 (s, 3H, OMe), 4.25 (dd, 1H, J 9.4 Hz, 11.3 Hz,H2); 4.40 (dd, 1H, J 3.8 Hz, 12.6 Hz, H2), 4.92 (bd, 1H, H4), 6.67 (d,1H, J 8.3 Hz, H6), 6.89 (d, 2H, J 8.7 Hz, ArH), 7.16 (d, 2H, J 8.7 Hz,ArH), 7.34 (d, 1H, J 8.3 Hz, H5).

Example 24 4′,7-Diacetoxy-3′-methoxy-8-methylisoflavan-4-ol

4′,7-Diacetoxy-3′-methoxy-8-methylisoflavan4-ol was prepared from4′,7-diacetoxy-3′-methoxy-8-methylisoflavone (0.25 g, 0.7 mmol) inmethanol (50 ml) using palladium-on-charcoal (5%, 0.07 g) by the methoddescribed above.

For trans-4′,7-diacetoxy-3′-methoxy-8-methylisoflavan4-ol; ¹H NMR(CDCl₃): δ 2.05 (s, 3H, CH₃), 2.30, 2.32 (each s, 3H, OCOCH₃), 3.18(ddd, 1H, J 3.8 Hz, 8.3 Hz, 11.4 Hz, H3), 3.79 (s, 3H, OMe), 4.28 (dd,1H, J 9.0 Hz, 11.3 Hz, H2); 4.41 (m, 1H, H2), 4.93 (d, 1H, J 7.9 Hz,H4), 6.64 (d, 1H, J 7.9 Hz, H6), 6.75-6.92 (m, ArH), 7.00 (d, 1H, J 7.9Hz, ArH), 7.16 (d, 1H, J 8.3 Hz, ArH).

For cis-3′,7-diacetoxy-8-methylisoflavan4-ol; ¹H NMR (CDCl₃): δ 2.05 (s,3H, CH₃), 2.30, 2.32 (each s, 3H, OCOCH₃), 3.29 (dt, 1H, J 3.4 Hz, J11.7 Hz, H3), 4.40 (m, 1H, H2); 4.59 (t, 1H, J 10.5 Hz, H2), 4.81 (bs,1H, H4), 6.67 (d, 1H, J 7.9 Hz, H6), 6.75-6.92 (m, ArH), 7.03 (d, 1H, J8.3 Hz, ArH), 7.33 (d, 1H, J 8.3 Hz, ArH).

Dehydration Reactions

Example 25 4′,7-Diacetoxydehydroequol (4′,7-Diacetoxyisoflav-3-ene)

Method A

Distilled trifluoroacetic acid (0.1 ml) was added to a solution of cis-and trans-4′,7-diacetoxytetrahydrodaidzein (0.1 g) in dry distilleddichloromethane (15 ml) and the mixture was refluxed under argon.Progress of the reaction was monitored by thin layer chromatography andfurther 0.1 ml portions of trifluoroacetic acid were added. Afterrefluxing for 4 hours, the reaction mixture was cooled and washedsuccessively with saturated sodium bicarbonate solution, water andbrine. The resulting organic phase was dried, concentrated,chromatographed and crystallised to yield 4′,7-diacetoxydehydroequol ascolourless prisms (0.034 g, 35%). ¹H NMR (CDCl₃+d₆-DMSO): δ 2.29 (s, 3H,OCOCH₃), 2.31 (s, 3H, OCOCH₃), 5.15 (s, 2H, H2), 6.62 (bs, 1H, H4), 6.65(dd, 1H, J 2.1 Hz 8.2 Hz, H6), 6.75 (bs, 1H, H8), 7.06 (d, 1H, J 8.2 HzH5), 7.12 (d, 2H, J 8.2 Hz, ArH), 7.43 (d, 2H, J 8.2 Hz, ArH).

Method B

p-Toluenesulfonic acid (0.02 g) was added to a solution of cis- andtrans-4′7-diacetoxytetrahydrodaidzein (0.1 g) in dry distilleddichloromethane (15 ml) and the mixture was refluxed under argon.Progress of the reaction was monitored by thin layer chromatography andafter 4 h at reflux, the reaction mixture was passed through a shortcolumn of silica gel and the eluant recrystallised from ethanol to yield4′,7-diacetoxydehydroequol as colourless prisms (0.025 g, 26%).

Method C

Phosphorous pentoxide (5 g) was added with stirring to a solution ofcis- and trans-4′,7-diacetoxytetrahydrodaidzein (1.0 g) in drydichoromethane (80 ml). The mixture was stirred at room temperature for2 hours and filtered through a pad of Celite. The dichoromethanesolution was concentrated and chromatographed on silica gel to yield4′,7-diacetoxydehydroequol as colourless prisms (0.64 g, 67%).

Example 26 7-Acetoxy4′-methoxyisoflav-3-ene

Phosphorus pentoxide (1.0 g) was added with stirring to a solution ofcis- and trans-7-acetoxy-4′-methoxyisoflavan-4-ol (0.1 g, 0.3 mmol) indry dichloromethane (20 ml). The mixture was stirred at room temperaturefor 2 hours and filtered through a pad of Celite. The organic phase wasconcentrated and chromatographed on silica gel to yield7-acetoxy-4′-methoxyisoflav-3-ene (0.04 g, 42%). 1H NMR (CDCl₃); δ 2.28(s, 3H, OCOCH3), 3.83 (s, 3, OCH3), 5.14 (s, 2H, H2), 6.61 (dd, 1H, J2.3 Hz 6.4 Hz, H6), 6.65 (d, 1H, J 2.3 Hz, H8), 6.69 (bs, 1H, H4), 6.92(d, 2H, J 9.0 Hz ArH), 7.04 (d, 1H, J 7.9 Hz, H5), 7.37 (d, 2H, J 9.0Hz, ArH).

Example 27 3′,7-Diacetoxydehydroequol (3′,7-Diacetoxyisoflav-3-ene)

3′,7-Diacetoxyisoflav-3-ene was prepared from cis- andtrans-3′,7-diacetoxyisoflavan-4-ol (0.2 g, 0.6 mmol) in drydichloromethane (50 ml) using phosphorus pentoxide (2.0 g). Yield: (0.09g, 48%). 1H NMR (CDCl₃): δ 2.29 and 2.32 (each s, 3H, OCOCH₃), 5.14 (s,2H, H2), 6.61 (d, 1H, J 2.3 Hz, H8), 6.66 (dd, 1H, J 2.3 Hz 7.9 Hz, H6),6.79 (bs, 1H, H4), 7.02-7.25 (m, 3H, ArH), 7.25-7.44 (m, 2H, ArH).

Example 28 7-Acetoxy-3′-methoxydehydroequol(7-Acetoxy-3′-methoxyisoflav-3-ene)

7-Acetoxy-3′-methoxyisoflav-3-ene was prepared from cis- andtrans-7-acetoxy-3′-methoxyisoflavan-4-ol (0.25 g, 0.8 mmol) in drydichloromethane (20 ml) using phosphorus pentoxide (2.0 g). Yield: (0.15g, 63%). ¹H NMR (CDCl₃): δ 2.28 (s, 3H, OCOCH₃), 3.85 (s, 3H, OMe), 5.15(s, 2H, H2), 6.60-6.67 (m, 2H, ArH), 6.78 (bs, 1H, H4), 6.84-7.06 (m,4H, ArH), 7.35 (t, 1H, J 8.6 Hz, ArH).

Example 29 4′,7-Diacetoxy-3′-methoxyisoflav-3-ene

4′,7-Diacetoxy-3′-methoxyisoflav-3-ene was prepared from cis- andtrans-4′,7-diacetoxy-3′-methoxyisoflavan-4-ol (0.20 g, 0.5 mmol) in drydichloromethane (20 ml) using phosphorus pentoxide (2.0 g). Yield: (0.1g, 58%).

Example 30 7-Acetoxyisoflav-3-ene

7-acetoxyisoflav-3-ene was prepared from cis- andtrans-7-acetoxyisoflavan4-ol (0.4 g, 1.4 mmol) in dry dichloromethane(60 ml) using phosphorus pentoxide (5.0 g). Yield: (0.2 g, 53%). ¹H NMR(CDCl₃): δ 2.29 (s, 3H, OCOCH₃), 5.18 (s, 2H, H2), 6.61-6.67 (m, 2H,ArH), 6.79 (bs, 1H, H4), 7.07 (d, 1H, J 7.9 Hz, H5), 7.23-7.45 (m, 5H,ArH).

Example 31 4′,7,8-Triacetoxydehydroequol(4′,7,8-Triacetoxyisoflav-3-ene)

Phosphorus pentoxide (5.0 g) was added with stirring to a solution ofcis- and trans4′,7,8-triacetoxyisoflavan-4-ol (0.5 g, 1.3 mmol) in drydichloromethane (50 ml). The mixture was stirred at room temperature for2 h and filtered through a pad of Celite. The resulting solution wasconcentrated and chromatographed on silica gel to yield4′,7,8-triacetoxyisoflav-3-ene (0.3 g, 63%). ¹H NMR (CDCl₃): δ 2.29,2.31, 2.32, (each s, 3H, OCOCH₃), 5.15 (s, 2H, H2), 6.72 (d, 1H, J 8.3Hz, H6), 6.75 (bs, 1H, H4), 6.97 (d, 1H, J 7.9 Hz, H5), 7.12 (d, 2H, J8.7 Hz ArH), 7.41 (d, 2H, J 8.7 Hz, ArH).

Example 32 7,8-Diacetoxy-4-methoxydehydroequol(7,8-Diacetoxy-4-methoxyisoflav-3-ene)

7,8-Diacetoxy4-methoxyisoflav-3-ene was prepared from cis- andtrans-7,8-diacetoxy-4-methoxyisoflavan-4-ol (0.4 g, 1.1 mmol) in drydichloromethane (60 ml) using phosphorus pentoxide (5.0 g). Yield: (0.18g, 47%). ¹H NMR (CDCl₃): δ 2.29, 2.32 (each s, 3H, OCOCH₃), 3.83 (s, 3H,OCH₃), 5.14 (s, 2H, H2), 6.69 (bs, 1H, H4), 6.71 (d, 1H, J 8.3 Hz, H6),6.90 (d, 2H, J 8.6 Hz ArH), 6.95 (d, 1H, J 7.9 Hz, H5), 7.36 (d, 2H, J8.6 Hz, ArH).

Example 33 4′,7-Diacetoxy-8-methylisoflav-3-ene

Phosphorus pentoxide (3.0 g) was added with stirring to a solution ofcis- and trans-4′,7-diacetoxy-8-methylisoflavan-4-ol (0.55 g, 1.5 mmol)in dry dichloromethane (25 ml). The mixture was stirred at roomtemperature for 2 h and filtered through a pad of Celite. The resultingsolution was concentrated and chromatographed on silica gel to yield4′,7-diacetoxy-8-methylisoflav-3-ene (0.25 g, 48%). m.p. 140° C. ¹H NMR(CDCl₃): δ 2.04 (s, 3H, CH₃), 2.31, 2.32 (each s, 3H, OCOCH₃), 5.16 (s,2H, H2), 6.61 (d, 1H, J 8.3 Hz, H6), 6.75 (bs, 1H, H4), 6.94 (d, 1H, J8.3 Hz, H5), 7.13 (d, 2H, J 8.7 Hz, ArH), 7.45 (d, 2H, J 8.7 Hz, ArH).Mass spectrum: m/z 339 (M+1, 6%); 338 (M, 26); 296 (48); 254 (90); 253(100).

Example 34 3′,7-Diacetoxy-8-methylisoflav-3-ene

3′,7-Diacetoxy-8-methylisoflav-3-ene was prepared from cis- andtrans-3′,7-diacetoxy-8-methylisoflavan-4-ol (0.25 g, 0.7 mmol) in drydichloromethane (20 ml) using phosphorus pentoxide (2.0 g). Yield: (0.13g, 54%) m.p. 116° C. ¹H NMR (CDCl₃): δ 2.04 (s, 3H, CH₃), 2.31, 2.32(each s, 3H, OCOCH₃), 5.16 (s, 2H, H2), 6.61 (d, 1H, J 8.3 Hz, H6), 6.79(bs, 1H, H4), 6.92 (d, 1H, J 8.3 Hz, ArH), 7.05 (dd, 1H, J 2.0 Hz, 8.0Hz, ArH), 7.15 (s, 1H, ArH), 7.26 (d, 1H, J 8.0 Hz, ArH), 7.37 (t, 1H, J8.0 Hz, ArH). Mass spectrum: m/z 339 (M+1, 15%); 338 (M, 22); 296 (54);254 (30).

Example 35 7-Acetoxy-4′-methoxy-8-methylisoflav-3-ene

7-Acetoxy4′-methoxy-8-methylisoflav-3-ene was prepared from cis- andtrans-7-acetoxy-4′-methoxy-8-methylisoflavan-4-ol (0.25 g, 0.7 mmol) indry dichloromethane (20 ml) using phosphorus pentoxide (2.0 g). Yield:(0.11 g, 46%) m.p. 107° C. ¹H NMR (CDCl₃): δ 2.04 (s, 3H, CH₃), 2.31 (s,3H, OCOCH₃), 3.83 (s, 3H, OMe), 5.16 (s, 2H, H2), 6.59 (d, 1H, J 8.3 Hz,H6), 6.68 (bs, 1H, H4), 6.90 (d, 1H, J 8.3 Hz, H5), 6.93 (d, 2H, J 9.0Hz, ArH), 7.37 (d, 2H, J 9.0 Hz, ArH). Mass spectrum: m/z 311 (M+1,13%); 310 (M, 68); 267 (100); 152 (68); 135 (90).

Example 36 4′,7-Diacetoxy-3′-methoxy-8-methylisoflav-3-ene

4′,7-Diacetoxy-3′-methoxy-8-methylisoflav-3-ene was prepared from cis-and trans-4′,7-diacetoxy-3′-methoxy-8-methylisoflavan4-ol (0.25 g, 0.6mmol) in dry dichloromethane (25 ml) using phosphorus pentoxide (2.0 g).Yield: (0.14 g, 58%) m.p. 123° C. ¹H NMR (CDCl₃): δ 2.05 (s, 3H, CH₃),2.31. 2.32 (each s, 3H, OCOCH₃), 3.88 (s, 3H, OMe), 5.16 (s, 2H, H2),6.61 (d, 1H, J 8.3 Hz, H6), 6.73 (bs, 1H, H4), 6.94 (d, 1H, J 8.3 Hz,H5), 6.97 (dd, 1H, J 1.9 Hz, 8.3 Hz, ArH), 7.03 (d, 1H, J 1.9 Hz, ArH),7.05 (d, 1H, J 7.9 Hz, ArH).

Deprotection Reactions

Example 37 Dehydroequol (Isoflav-3-ene4′,7-diol)

Imidazole (0.09 g) was added to a suspension of4′,7-diacetoxydehydroequol (0.03 g, 0.09 mmol) in absolute ethanol (2.0ml) and the mixture was refluxed for 45 min under argon. The solutionwas concentrated under reduced pressure and the product was precipitatedby addition of distilled water (10 ml). The mixture was left overnightin the fridge and filtered to yield dehydroequol. The crude product wasreprecipitated from methanol by addition of benzene to yielddehydroequol as fluffy white solid (0.012 g, 55%). ¹H NMR(CDCl₃+d₆-DMSO): δ 4.93 (s, 2H, H2), 6.26 (bs, 1H, H4), 6.29 (dd, 1H, J2.0 Hz, 8.2 Hz, H6), 6.50 (bs, 1H, H8), 6.73 (d, 2H, J 8.2 Hz, ArH),6.76 (d, 2H, J 8.2 Hz, H5), 7.13 (d, 2H, J 8.2 Hz, ArH).

Example 38 7-Hydroxy-4′-methoxyisoflav-3-ene

Imidazole (0.18 g) was added to a suspension of7-acetoxy-4′-methoxyisoflav-3-ene (0.06 g, 0.02 mmol) in absoluteethanol (5.0 ml) and the mixture was refluxed for 45 minutes underargon. The solution was concentrated under reduced pressure and theproduct was precipitated by addition of distilled water (10 ml). Themixture was left overnight in the fridge and filtered to yieldisoflav-3-ene. The crude product was recrystallised frommethanol/benzene to yield 7-hydroxy4′-methoxyisoflav-3-ene (0.034 g,66%). ¹H NMR (CDCl₃+d₆-DMSO): δ 3.74 (s, 31H, OCH₃), 4.99 (s, 2H, H2),6.21 (d, 1H, J 2.3 Hz, H8), 6.29 (dd, 1H, J 2.3 Hz, 8.3 Hz, H6), 6.67(bs, 1H, H4), 6.85 (d, 1H, J 8.3 Hz, H5 ), 6.86 (d, 2H, J 8.7 Hz, ArH),7.33 (d, 2H, J 8.7 Hz, ArH).

Example 39 Isoflav-3-ene-3′,7-diol

Isoflav-3-ene-3′,7-diol was prepared from 3′,7-diacetoxyisoflav-3-ene(0.09 g, 0.3 mmol) and imidazole (0.3 g) in ethanol (2.0 ml) asdescribed for isoflav-3-ene-4′,7-diol. Yield: (0.04 g, 60%). ¹H NMR(CDCl₃+d₆-DMSO): δ 4.94 (s, 2H, H2), 6.21 (d, 1H, J 2.0 Hz, H8), 6.29(dd, 1H, J 2.3 Hz, 8.3 Hz, H6), 6.62 (m, 1H, ArH), 6.64 (bs, 1H, H4),6.75-6.82 (m, 3H, ArH), 7.07 (t, 1H, J 7.9 Hz, ArH), 8.99-9.17 (bs, 2H,OH).

Example 40 3′-Methoxylsoflav-3-ene-7-ol

3′-Methoxylsoflav-3-ene-7-ol was prepared from7-acetoxy-3′-methoxyisoflav-3-ene (0.1 g, 0.3 mmol) and imidazole (0.15g) in ethanol (2.0 ml) as described for isoflav-3-ene-4′,7-diol. Yield:(0.06 g, 70%) m.p. 75° C. 1H NMR (CDCl₃): δ 3.84 (s, 3H, OMe), 5.12 (s,2H, H2), 6.38 (d, 1H, J 2.0 Hz, H8), 6.40 (dd, 1H, J 2.0 Hz, 8.3 Hz,H6), 6.76 (bs, 1H, H4), 6.84 (dd, 1H, J 1.9 Hz, 8.3 Hz, ArH), 6.95 (m,3H, ArH), 7.29 (t, 1H, J 8.3 Hz, ArH).

Example 41 3′-Methoxylsoflav-3-ene-4′,7-diol

3′-Methoxylsoflav-3-ene4′,7-diol was prepared from4′,7-diacetoxy-3-methoxyisoflav-3-ene (0.11 g, 0.3 mmol) and imidazole(0.3 g) in ethanol (2.0 ml) as described for isoflav-3-ene-4′,7-diol.Yield: (0.06 g, 71%). ¹H NMR (d₆-acetone): δ 3.90 (s, 3H, OMe), 5.07 (s,2H, H2), 6.31 (d, 1H, J 2.3 Hz, H8), 6.40 (dd, 1H, J 2.3 Hz, 8.3 Hz,H6), 6.78 (bs, 1H, H4), 6.83 (d, 1H, J 8.3 Hz, ArH), 6.92 (dd, 2H, J 1.9Hz, 8.3 Hz, ArH), 7.14 (d, 1H, J 1.9 Hz, ArH), 7.04,7.63 (each s, 1H,OH).

Example 42 Isoflav-3-ene-7-ol

Isoflav-3-ene-7-ol was prepared from 7-acetoxyisoflav-3-ene (0.2 g, 0.75mmol) and imidazole (0.24 g) in ethanol (3.5 ml) as described forisoflav-3-ene4′,7-diol. Yield: (0.11 g, 66%) m.p. 120° C. ¹H NMR(d₆-DMSO): δ 5.07 (s, 2H, H2), 6.24 (d, 1H, J 2.2 Hz, H8), 6.33 (dd, 1H,J 1.9 Hz, 7.9 Hz, H6), 6.96 (d, 1H, J 7.9 Hz, H5), 7.00 (s, 1H, H4),7.26-7.47 (m, 5H, ArH), 9.65 (bs, 1H, OH). Mass spectrum: m/z 224 (m,74%); 223 (100), 175 (28); 165 (23); 147 (41).

Example 43 Isoflav-3-ene-4′,7,8-triol

Imidazole (0.6 g) was added to a suspension of4′,7,8-triacetoxyisoflav-3-ene (0.16 g, 0.4 mmol) in absolute ethanol(5.0 ml) and the mixture was refluxed for 45 min under argon. Thesolution was concentrated under reduced pressure and the product wasprecipitated by addition of distilled water (10 ml). The mixture wasleft overnight in the fridge and filtered to yield isoflav-3-ene. Thecrude product was recrystallised from methanol/benzene to yieldIsoflav-3-ene-4′,7-8-triol (0.08 g, 75%). ¹H NMR (CDCl₃+d₆-DMSO): δ 4.97(s, 2H, H2), 6.30 (d, 1H, J 8.2 Hz, H6), 6.36 (d, 1H, J 8.3 Hz, H5),6.55 (bs, 1H, H4), 6.72 (d, 1H, J 8.7 Hz, ArH), 7.17 (d, 2H, J 8.7 Hz,ArH).

Example 44 4′-Methoxyisoflav-3-ene-7,8-diol

4′-Methoxyisoflav-3-ene-7,8-diol was prepared from7,8-diacetoxy-4-methoxyisoflav-3-ene (0.15 g, 0.4 mmol) and imidazole(0.4 g) in ethanol (1.6 ml) as described for isoflav-3-ene-4′,7-8-triol.Yield: (0.73 g, 61%). ¹H NMR (CDCl₃+d₆-DMSO): δ 3.83 (s, 3H, OCH₃), 5.15(s, 2H, H2), 6.51 (d, 1H, J 8.3 Hz, H6), 6.58 (d, 1H, J 8.3 Hz, H5),6.68 (bs, 1H, H4), 6.92 (d, 1H, J 8.7 Hz, ArH), 7.35 (d, 2H, J 8.7 Hz,ArH). Mass spectrum: m/z 270 (M, 5%); 256 (100); 255 (70); 239 (20); 181(25).

Example 45 8-Methylisoflav-3-ene4′,7-diol

Imidazole (0.6 g) was added to a suspension of4′,7-diacetoxy-8-methylisoflav-3-ene (0.25 g, 0.7 mmol) in absoluteethanol (5.0 ml) and the mixture was refluxed for 45 min under argon.The solution was concentrated under reduced pressure and the product wasprecipitated by addition of distilled water (10 ml). The mixture wasleft overnight in the fridge and filtered to yield isoflav-3-ene. Thecrude product was recrystallised from methanol/benzene to yield8-methylisoflav-3-ene-4′,7-diol (0.13 g, 68%). m.p. 190-93° C. ¹H NMR(CDCl₃+d₆-DMSO): δ 1.94 (s, 3H, CH₃), 4.98 (s, 2H, H2), 6.32 (d, 1H, J7.9 Hz, H6), 6.58 (bs, 1H, H4), 6.67 (bd, 1H, H5), 6.72 (d, 2H, J 8.7Hz, ArH), 7.21 (bd, 2H, ArH). Mass spectrum: m/z 255 (M+1, 16%); 254 (M,79); 253 (100); 161 (32).

Example 46 8-Methylisoflav-3-ene-3′,7-diol

8-Methylisoflav-3-ene-3′,7-diol was prepared from3′,7-diacetoxy-8-methylisoflav-3-ene (0.12 g, 0.4 mmol) and imidazole(0.3 g) in ethanol (2.5 ml) as described for8-methylisoflav-3-ene-4′,7-diol. Yield: (0.07 g, 77%) m.p. 130° C. ¹HNMR (CDCl₃+d₆-DMSO): δ 1.95 (s, 3H, CH₃), 4.98 (s, 2H, H2), 6.34 (d, 1H,J 8.0 Hz, H6), 6.61-6.94 (m, 5H, ArH), 7.08 (bt, 1H, ArH). Massspectrum: m/z 254 (M, 100%); 253 (96); 161 (45).

Example 47 4′-Methoxy-8-methylisoflav-3-ene-7-ol

4′-Methoxy-8-methylisoflav-3-ene-7-ol was prepared from7-acetoxy-4′-methoxy-8-methylisoflav-3-ene (0.11 g, 0.3 mmol) andimidazole (0.14 g) in ethanol (1.5 ml) as described for8-methylisoflav-3-ene-4′,7-diol. Yield: (0.05 g, 53%) m.p. 103° C. ¹HNMR (d₆-acetone): δ 1.99 (s, 3H, CH₃), 3.81 (s, 3H, OMe), 5.11 (s, 2H,H2), 6.43 (d, 1H, J 8.3 Hz, H6), 6.77 (bs, 1H, H4), 6.80 (d, 1H, J 8.3Hz, H5), 6.95 (d, 2H, J 9.0 Hz, ArH), 7.44 (d, 2H, J 9.0 Hz, ArH). Massspectrum: 282 (M, 9%); 267 (100); 268 (95); 134 (52).

Example 48 3′-Methoxy-8-methylisoflav-3-ene4′,7-diol

3′-Methoxy-8-methylisoflav-3-ene-4′,7-diol was prepared from4′,7-diacetoxy-3′-methoxy-8-methylisoflav-3-ene (0.21 g, 0.6 mmol) andimidazole (0.52 g) in ethanol (4 ml) as described for8-methylisoflav-3-ene4′,7-diol. Yield: (0.1 g, 63%). ¹H NMR (CDCl₃): δ2.14 (s, 3aH, CH₃), 3.94 (s, 3H, OMe), 5.11 (s, 2H, H2), 6.42 (d, 1H, J8.3 Hz, H6), 6.64 (bs, 1H, ArH), 6.80 (d, 1H, J 7.9 Hz, ArH), 6.94 (m,2H, ArH), 7.12 (m, 1H, ArH), 7.26, 7.70 (each bs, 1H, OH).

Deprotection Reactions

Example 49 cis- and trans-Tetrahydrodaidzein

Imidazole (0.2 g) was added to a suspension of4′,7-diacetoxytetrahyrodaidzein (0.10 g, 0.3 mmol) in absolute ethanol(4.0 ml) and the mixture refluxed for 45 min under argon. The solutionwas concentrated under reduced pressure and distilled water (10 ml) wasadded. The mixture was left overnight in the fridge and the crystallineproduct was filtered to yield cis- and trans-tetrahydrodaidzein (0.06 g,80%).

Example 50 trans-Tetrahydrodaidzein (trans-4′,7-Dihydroxyisoflavan-4-ol)

Trans-4′,7-dihydroxyisoflavan-4-ol was prepared fromtrans4′,7-dihydroxyisoflavan-4-ol and imidazole in ethanol as describedfor cis- and trans-tetrahydrodaidzein. ¹H NMR (d₆-acetone): δ 2.99 (ddd,1H, J 3.4 Hz, 6.8 Hz, 10.6 Hz, H3), 4.13 (dd, 1H, J 7.0 Hz, 10.9 Hz,H2); 4.24 (dd, 1H, J 3.8 Hz, 11.3 Hz, H2), 4.70 (d, 1H, J 6.4 Hz, H4),6.20 (d, 1H, J 2.6 Hz, H8), 6.38 (dd, 1H, J 2.3 Hz, 8.3 Hz, H6), 6.71(d, 2H, J 8.7 Hz, ArH), 7.04 (d, 2H, J 8.7 Hz, ArH), 7.18 (d, 1H, J 8.3Hz, H5).

Example 51 cis- and trans-7-Hydroxy-4′-methoxyisoflavan-4-ol

Imidazole (0.4 g) was added to a suspension of7-acetoxy-4′-methoxyisoflavan-4-ol (0.20 g, 0.6 mmol) in absoluteethanol (8.0 ml) and the mixture refluxed for 45 minutes under argon.The solution was concentrated under reduced pressure and distilled water(10 ml) was added. The mixture was left overnight in the fridge and thecrystalline product was filtered to yield cis- andtrans-7-hydroxy-4′-methoxyisoflavan-4-ol (0.16 g, 79%).

Example 52 cis- and trans-7-Hydroxyisoflavan4-ol

7-hydroxyisoflavan-4-ol was prepared from 7-acetoxyisoflavan-4-ol (0.14g, 0.5 mmol) and Imidazole (0.1 7 g) in ethanol (3.0 ml) as describedfor cis- and trans-tetrahydrodaidzein.

For trans-7-hydroxyisoflavan-4-ol; ¹H NMR (d₆-acetone): δ 3.08 (m, 1H,H3), 4.00 (t, 1 H, J 10.2 Hz, H2); 4.30 (m, 1H, H2), 4.81 (d, 1H, J 7.2Hz, H4), 6.25-6.43 (m, ArH), 6.89 (d, J 8.3 Hz, ArH), 7.07 (d, J 8.3 Hz,ArH), 7.22-7.64 (m, ArH).

For cis-7-acetoxyisoflavan-4-ol; ¹H NMR (d₆-acetone): δ 3.20 (m, 1H,H3), 4.36 (m, 1H, H2); 4.57 (dd, 1H, J 10.2 Hz, 12.0 Hz, H2), 4.68 (bs,1H, H4), 6.25-6.43 (m, ArH), 6.89 (d, J 8.3 Hz, ArH), 7.07 (d, J 8.3 Hz,ArH), 7.22-7.64 (m, ArH).

Example 53 cis- and trans-4′,7-Dihydroxy-8-methylisoflavan-4ol

4′,7-Dihydroxy-8-methylisoflavan-4-ol was prepared from4′,7-diacetoxy-8-methylisoflavan-4-ol (0.4 g, 1.1 mmol) and imidazole(1.0 g) in ethanol (7.0 ml) as described for cis- andtrans-tetrahydrodaidzein.

For trans-4′,7-dihydroxy-8-methylisoflavan-4-ol; ¹H NMR (d₆-acetone): δ1.98 (s, 3H, CH₃), 2.98 (ddd, 1H, J 3.8 Hz, 10.9 Hz, 12.0 Hz, H3), 4.18(m, 1H, H2); 4.27 (m, 1H, H2), 4.75 (d, 1H, J 6.4 Hz, H4), 6.42 (m,ArH), 6.75 (m, ArH), 7.05-7.19 (m, ArH), 7.66 (bs, OH).

For cis4′,7-dihydroxy-8-methylisoflavan4-ol; ¹H NMR (d₆-acetone): δ 1.99(s, 3H, CH₃), 3.01 (dt, 1H, J 3.4 Hz, 12.0 Hz, H3), 4.31 (m, 1H, H2);4.52 (dd, 1H, J 10.2 Hz, 12.0 Hz, H2), 4.60 (bs, 1H, H4), 6.42 (m, ArH),6.75 (m, ArH), 7.05-7.19 (m, ArH), 7.66 (bs, OH).

Example 54 trans-7-Hydroxy-4′-methoxy-8-methylisoflavan-4-ol

trans-7-Hydroxy-4′-methoxy-8-methylisoflavan-4-ol was prepared fromtrans-7-acetoxy4′-methoxy-8-methylisoflavan-4-ol (0.23 g, 0.7 mmol) andimidazole (0.28 g) in ethanol (2.1 ml) as described for cis- andtrans-tetrahydrodaidzein. m.p. 162° C. Mass spectrum: 285 M, 5%); 268(10); 151 (20); 135 (20); 134 (100); 119 (20). ¹H NMR (d-₆-acetone): δ1.97 (s, 3H, CH₃), 3.00 (ddd, 1H, J 3.4 Hz, 7.2 Hz, 10.2 Hz, H3), 3.72(s, 3H, OMe), 4.20 (dd, 1H, J 7.5 Hz, 10.9 Hz, H2); 4.27 (m, 1H, H2),4.73 (d, 1H, J 6.8 Hz, H4), 6.45 (d, 1H, J 8.3 Hz, H6), 6.85 (d, 2H, J8.6 Hz, ArH), 7.10 (d, 1H, J 8.7 Hz, H5), 7.18 (d, 2H, J 8.6 Hz, ArH).

Hydrogenation Reactions:—Isoflavone″cis-Isoflavan-4-ol

Example 55 cis-4′,7-Diacetoxyisoflavan-4-ol

Platinum(IV)oxide (Adam's catalyst) (0.05 g) was added to a solution ofof 4′,7-diacetoxyisoflavanone (0.25 g, 0.7 mmol) in ethyl acetate (40ml) and the mixture was stirred at room temperature under a hydrogenatmosphere for 55 h. The catalyst was removed by filtration throughCelite and the filtrate was evaporated in vacuo to yield predominantlythe cis-4′,7-diacetoxyisoflavan-4-ol.

For cis-4′,7-diacetoxyisoflavan-4-ol; ¹H NMR (CDCl₃): δ 2.28 (s, 3H,OCOCH₃), 2.29 (s, 3H, OCOCH₃), 3.30 (dt, 1H, J 3.4 Hz, J 11.8 Hz, H3),4.31 (ddd, 1H, J 1.4 Hz, 3.6 Hz, 10.5 Hz, H2); 4.56 (dd, 1H, J 10.5 Hz,11.8 Hz, H2), 4.75 (dd, 1H, J 1.3 Hz, 3.2 Hz, H4), 666 (dd, 1H, J 2.3Hz, 8.7 Hz, H6),6.69 (d, 1H, J 2.3 Hz, H8), 7.08 (d, 2H, J 8.6 Hz, ArH),7.26 (d, 1H, 8.4 Hz, H5), 7.29 (d, 2H, J 8.6 Hz, ArH). ¹³C NMR (CDCl₃):δ 20.98 (OCOCH ₃), 43.52 (C3), 64.10 (C2), 66.46 (C4), 110.08 (C6),114.09 (C8), 121.82, 129.40 (OCOCH₃), 131.10 (C5).

Hydrogenation Reactions:—Isoflavone→Isoflavan4-one

Example 56 4′,7-Diacetoxydihydrodaidzein (4′,7-Diacetoxyisoflavan-4-one)

Palladium-on-charcoal (5%, 0.02 g) was added to a solution of4′,7-diacetoxydaidzein (0.50 g, 1.5 mmol) in ethyl acetate (80 ml) andthe mixture was stirred at room temperature under a hydrogen atmospherefor 72 h. The catalyst was removed by filtration through Celite and theresulting filtrate was evaporated in vacuo. The residue wasrecrystallised from ethanol to yield 4′,7-diacetoxydihydrodaidzein (0.40g, 80%) as colotirless )lates. ¹H NMR (CDCl₃): δ 2.29 (s, 3H, OCOCH₃),2.23 (s, 3H, OCOCH₃), 3.98 (dd, 1H, J 6.2 Hz, 8.2 Hz, H3), 4.69 (m, 2H,H2), 6.78-6.82 (m, 2H, ArH), 7.08 (d, 2H, J 9.2 Hz, ArH), 7.30 (d, 2H, J8.2 Hz, ArH), 7.98 (d, 1H, J 9.2 Hz H5).

Hydrogenation Reactions:—Isoflavan-3-ene→Isoflavan

Example 57 O,O-Diacetylequol

Palladium-on-charcoal (5%, 0.02 g) was added to a solution of4′,7-diacetoxyisoflav-3-ene (0.20 g, 0.06 ml) in ethyl acetate (60 ml)and the mixture was stirred at room temperature under a hydrogenatmosphere for 24 h. The catalyst was removed by filtration throughCelite and the resulting filtrate was evaporated in vacuo. The residuewas recrystallised from dichloromethane/light petroleum to yieldO,O-diacetylequol (0.15 g, 75%). ¹H NMR (CDCl₃): δ 2.29 (s, 3H, OCOCH₃),2.31 (s, 3H, OCOCH₃), 3.00 (d, 2H, J 8.3 Hz, H4), 3.25 (m, 1H, H3), 4.00(t, 1H, H2), 4.34 (dd, 1H, J 3.4 Hz, 10.9 Hz, H2), 6.61 (d, J 7.5 Hz,1H, ArH), 6.60 (s, 1H, ArH), 7.06 (bd, 3H, J 8.3 Hz, ArH), 7.24 (d, 3H,J 8.3 Hz, ArH).

Deprotection Reactions

Example 58 Dihydrodaidzein (4′,7-Dihydroxyisoflavan4-one)

Imidazole (0.63 g) was added to a suspension of4′,7-diacetoxydihydrodaidzein (0.26 g, 0.08 mmol) in absolute ethanol(5.0 ml) and the mixture was refluxed for 45 min under argon.

The solution was concentrated under reduced pressure and distilled water(10 ml) was added to the residue. The mixture was left overnight in thefridge and the resulting precipitate was filtered. The crude product wasrecrystallised from ethyl aceate/dichloromethane to yield4′,7-diacetoxydihydrodaidzein (0.14 g, 71%) as a white powder. ¹H NMR(d₆-acetone): δ 3.83 (t, 1H, J 7.2 Hz, H3), 4.60 (d, 2H, J 6.2 Hz, 1H2),6.39 (d, 1H, J 2.0 Hz, H8), 6.55 (dd, 1H, J 8.2, J 2.0 Hz, ArH), 6.80(d, 2H, J 8.2 Hz, ArH), 7.10 (d, 1H, J 8.2 Hz, ArH), 7.74 (d, 1H, J 8.2Hz, H5).

Example 59 Equol (4′,7-Dihydroxyisoflavan)

Imidazole 0.5 g) was added to a suspension of (O,O-diacetylequol (0.15g, 0.08 mmol) in absolute ethanol (5.0 ml) and the mixture was refluxedfor 45 min under argon. The solution was concentrated under reducedpressure and distilled water (10 ml) was added to the residue. Themixture was left overnight in the fridge and the resulting product wasfiltered to yield equol (0.09 g, 80%) as a white powder. ¹H NMR(d₆-DMSO): δ 2.70 (d, 2H, J 9.2 Hz, H4), 2.92 (m, 1H, H3), 3.73 (t, 1H,J 10.3 Hz, H2), 4.06 (dd, 1H, J 3.0 Hz, 11.2 Hz, H2), 6.16 (bs, 1H,ArH), 6.21 (bd, J 8.2 Hz, 1H, ArH), 6.63 (d, 2H, J 8.2 Hz, ArH), 6.69 d,1H, J 8.2 Hz, ArH), 6.87 (d, 2H, J 8.2 Hz, ArH)

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described. It is to be understood that the inventionincludes all such variations and modifications. The inventions alsoincludes all of the steps, features, compositions and compounds referredto or indicated in the specification, individually or collectively, andany and all combinations of any two or more of said steps or features.

1. A method for the preparation of a compound of formula II

wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ are independently hydrogen,hydroxy, OR₉, OC(O)R₉, OS(O)R₉, alkyl, haloalkyl, aryl, arylalkyl, thio,alkylthio, amino, alkylamino, dialkylamino, nitro, or halo, and R₉ isalkyl, haloalkyl, aryl, arylalkyl or alkylaryl, comprising the step ofhydrogenating a compound of formula I

wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈ and R₉ are as defined above toprepare a compound of formula II.
 2. A method of claim 1, wherein thehydrogenation step is performed with hydrogen in the presence of areduction catalyst and a solvent.
 3. A method of claim 2, wherein thereduction catalyst comprises palladium, palladium hydroxide, platinum orplatinum oxide.
 4. A method of claim 3, wherein the reduction catalystis palladium on activated carbon, palladium on barium sulfate orplatinum(IV)oxide.
 5. A method of claim 4, wherein the reductioncatalyst is palladium on activated carbon (1% Pd to 10% Pd).
 6. A methodof claim 5, wherein the reduction catalyst is about 5% palladium onactivated carbon.
 7. A method of claim 2, wherein the solvent is a C₁-C₈alcohol, an alkyl acetate or a C₁-C₃ carboxylic acid.
 8. A method ofclaim 7, wherein the solvent is a methanol, ethanol or C₁-C₆ alkylacetate.
 9. A method of claim 8, wherein the solvent is absolutemethanol or absolute ethanol.
 10. A method of claim 1 which furthercomprises the step of dehydrating and optionally deprotecting ortransforming a compound of formula II to prepare a compound of formulaIII

R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ are independently hydrogen, hydroxy,OR₉, OC(O)R₉, OS(O)R₉, alkyl, haloalkyl, aryl, arylalkyl, thio,alkylthio, amino, alkylamino, dialkylamino, nitro, or halo, and R₉ isalkyl, haloalkyl, aryl, arylalkyl or alkylaryl.
 11. A method of any oneof claims 1 to 10, wherein the compounds of formula I, II or III havethe following substituents R₁ is hydroxy, OR₉ or OC(O)R₉, R₂, R₃, R₄,R₅, R₆ and R₇ are independently hydrogen, hydroxy, OR₉, OC(O)R₉, alkyl,aryl or arylalkyl, R₈ is hydrogen, and R₉ is methyl, ethyl, propyl,isopropyl or trifluoromethyl.
 12. A method of claim 11, wherein thecompounds of formula I, II or III have the following substituents R₁ ishydroxy, OR₉ or OC(O)R₉, R₂, R₃, R₄, R₅ and R₇ are independentlyhydrogen, hydroxy, OR₉, OC(O)R₉, alkyl, aryl or arylalkyl, R₆ and R₈ arehydrogen, and R₉ is methyl.
 13. A method of any one of claims 1 to 12,wherein the compound of formula I is 4′,7-diacetoxyisoflavone (daidzeindiacetate) or 7-acetoxy-4′-methoxyisoflavone.
 14. A method of any one ofclaims 1 to 13, wherein the compound of formula II is4′,7-diacetoxyisoflavan-4-ol (tetrahydrodaidzein diacetate) or7-acetoxy4′-methoxyisoflavan-4-ol.
 15. A method of any one of claims 10to 14, wherein and the compound of formula III is4′,7-diacetoxyisoflav-3-ene (dehydroequol diacetate),4′,7-dihydroxyisoflav-3-ene (dehydroequol),7-acetoxy-4′-methoxyisoflav-3-ene or 7-hydroxy-4′-methoxyisoflav-3-ene.16. A method for the preparation of a compound of formula IV

wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ are independently hydrogen,hydroxy, OR₉, OC(O)R₉, OS(O)R₉, alkyl, haloalkyl, aryl, arylalkyl, thio,alkylthio, amino, alkylamino, dialkylamino, nitro, or halo, and R₉ isalkyl, haloalkyl, aryl, arylalkyl or alkylaryl, comprising the step ofhydrogenating a compound of formula I

wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈ and R₉ are as defined above toprepare a compound of formula IV.
 17. A method of claim 16, wherein thehydrogenation step is performed with hydrogen in the presence of areduction catalyst and a solvent.
 18. A method of claim 17, wherein thereduction catalyst comprises palladium, palladium hydroxide, platinum orplatinum(IV)oxide.
 19. A method of claim 18, wherein the reductioncatalyst is palladium on activated carbon (1% Pd to 10% Pd).
 20. Amethod of claim 19, wherein the reduction catalyst is about 5% palladiumon activated carbon.
 21. A method of claim 17, wherein the solvent is aC₁-C₈ alcohol, a C₁-C₆ alkyl acetate or a C₁-C₃ carboxylic acid.
 22. Amethod of claim 21, wherein the solvent is absolute methanol, ethanol orethyl acetate.
 23. A method of any one of claims 16 to 22, wherein thecompound of formula I is 4′,7-diacetoxyisoflavone (daidzein diacetate)or 7-acetoxy-4′-methoxyisoflavone.
 24. A method of any one of claims 16to 22, wherein the compound of formula IV has the following substituentsR₁ is hydroxy, OR₉ or OC(O)R₉, R₂, R₃, R₄, R₅, R_(6 l and R) ₇ areindependently hydrogen, hydroxy, OR₉, OC(O)R₉, alkyl, aryl or arylalkyl,R₈ is hydrogen, and R₉ is methyl, ethyl, propyl, isopropyl ortrifluoromethyl.
 25. A method of claim 24, wherein the compound offormula IV has the following substituents R₁ is hydroxy, OR₉ or OC(O)R₉,R₂, R₃, R₄, R₅ and R₇ are independently hydrogen, hydroxy, OR₉, OC(O)R₉,alkyl, aryl or arylalkyl, R₆ and R₈ are hydrogen, and R₉ is methyl. 26.A method of claim 25, wherein the compound of formula IV is4′,7-diacetoxyisoflavan-4-one (diacetoxydihydrodaidzein) or4′,7-dihydroxyisoflavan-4-one (dihydrodaidzein).
 27. A method for thepreparation of a compound of formula V

wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ are independently hydrogen,hydroxy, OR₉, OC(O)R₉, OS(O)R₉, alkyl, haloalkyl, aryl, arylalkyl, thio,alkylthio, amino, alkylamino, dialkylamino, nitro, or halo, and R₉ isalkyl, haloalkyl, aryl, arylalkyl or alkylaryl, comprising the step ofhydrogenating a compound of formula III

wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈ and R₉ are as defined above toprepare a compound of formula V.
 28. A method of claim 27, wherein thehydrogenation step is performed with hydrogen in the presence of areduction catalyst and a solvent.
 29. A method of claim 28, wherein thereduction catalyst comprises palladium, palladium hydroxide, platinum orplatinum(IV)oxide.
 30. A method of claim 29, wherein the reductioncatalyst is palladium on activated carbon (1% Pd to 10% Pd).
 31. Amethod of claim 30, wherein the reduction catalyst is about 5% palladiumon activated carbon.
 32. A method of claim 28, wherein the solvent is aC₁-C₈ alcohol, a C₁-C₆ alkyl acetate or a C₁-C₃ carboxylic acid.
 33. Amethod of claim 32, wherein the solvent is a methanol, ethanol or ethylacetate.
 34. A method of claim 33, wherein the solvent is ethyl acetate.35. A method of any one of claims 27 to 34, wherein and the compound offormula III is 4′,7-diacetoxyisoflav-3-ene (dehydroequol diacetate),4′,7-dihydroxyisoflav-3-ene (dehydroequol),7-acetoxy4′-methoxyisoflav-3-ene or 7-hydroxy-4′-methoxyisoflav-3-ene.36. A method of any one of claims 27 to 34, wherein the compound offormula V has the following substituents R₁ is hydroxy, OR₉ or OC(O)R₉,R₂, R₃, R₄, R₅, R₆ and R₇ are independently hydrogen, hydroxy, OR₉,OC(O)R₉, alkyl, aryl or arylalkyl, R₈ is hydrogen, and R₉ is methyl,ethyl, propyl, isopropyl or trifluoromethyl.
 37. A method of claim 36,wherein the compound of formula V has the following substituents R₁ ishydroxy, OR₉ or OC(O)R₉, R₂, R₃, R₄, R₅ and R₇ are independentlyhydrogen, hydroxy, OR₉, OC(O)R₉, alkyl, aryl or arylalkyl, R₆ and R₈ arehydrogen, and R₉ is methyl.
 38. A method of claim 37, wherein thecompound of formula V is 4′,7-diacetoxyisoflavan (equol diacetate) or4′,7-dihydroxyisoflavan (equol).
 39. Methods substantially ashereinbefore described especially with reference to the Examples. 40.Compounds of formula II or formula III or formula IV or formula V whenprepared by a method of any preceding claim.
 41. A compound of theformulae II, III, IV or V, wherein R₁ is hydroxy, OR₉, OC(O)R₉, thio,alkylthio, or halo, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ are independentlyhydrogen, hydroxy, OR₉, OC(O)R₉, OS(O)R₉, alkyl, aryl, thio, alkylthioor halo, and R₉ is alkyl, fluoroalkyl or arylalkyl with the proviso thatat least one of R₅, R₆ and R₇ is not hydrogen, or when R₅, R₆ and R₇ areall hydrogen, then R₃ is hydroxy, OR₉, OC(O)R₉, OS(O)R₉, alkyl aryl,thio, alkylthio or halo, provided that compounds of the formula

wherein R₁ is hydroxy or acetoxy, R₂ is hydrogen, hydroxy, acetoxy,methoxy, methyl, isopropyl or halo, R₃ is hydrogen, methoxy, methyl,halo or trifluoromethyl, R₆ is hydrogen, hydroxy or acetoxy, and R₇ ishydrogen, hydroxy, methyl or methoxy are specifically excluded, providedthat compounds of the formula

wherein R₃ is hydroxy or methoxy, and R₄ is hydrogen or methoxy arespecifically excluded, provided that compounds of the formulae

wherein R₁ is hydroxy, methoxy, ethoxy, methylthio or halogen, and R₂,R₃ R₄, R₅, R₆, and R₇ are independently hydrogen, hydroxy, methoxy,ethoxy, methylthio or halogen, are specifically excluded, and providedthat the compounds 4′,7-Dihydroxy-3 ′,5′-dimethoxyisoflavan-4-one4′,5-Dimethoxy-7-hydroxy-8-methylisoflavan-4-one2′,7-Dihydroxy-4′,8-dimethoxyisoflavan-3 -ene are specifically excluded.42. A compound of claim 41, wherein R₁ is hydroxy, OR₉ or OC(O)R₉, R₂and R₃ are independently hydrogen, hydroxy, OR₉ or OC(O)R₉, R₄, R₅, R₆,and R₈ are hydrogen, R₇ is hydroxy, OR₉, OC(O)R₉, alkyl, aryl or halo,and R₉ is methyl, ethyl, propyl, isopropyl, trifluoromethyl or benzyl.43. A compound of claim 41, wherein R₁ is hydroxy, OR₉ or OC(O)R₉, R₂and R₃ are independently hydrogen, hydroxy, OR₉ or OC(O)R₉, R₅ is OR₉,OC(O)R₉, alkyl, aryl or halo, R₄, R₆, R₇, and R₈ are hydrogen, and R₉ ismethyl, ethyl, propyl, isopropyl, trifluoromethyl or benzyl.
 44. Acompound of formula I selected from the group consisting of:4′,7,8-Triacetoxyisoflavone 7,8-Diacetoxy-4′-methoxyisoflavone4′,7-Diacetoxy-8-methylisoflavone 3′,7-Diacetoxy-8-methylisoflavone7-Acetoxy-4′-methoxy-8-methylisoflavone 4′,7-Diacetoxy-3′-methoxy-8-methylisoflavone 4′,5,7-Triacetoxyisoflavone
 45. A compoundof formula II selected from the group consisting of:4′,7,8-Triacetoxyisoflavan-4-ol 7,8-Diacetoxy-4-methoxyisoflavan-4-ol4′,7-Diacetoxy-8-methylisoflavan-4-ol3′,7-Diacetoxy-8-methylisoflavan-4-ol7-Acetoxy-4′-methoxy-8-methylisoflavan-4-ol4′,7-Diacetoxy-3′-methoxy-8-methylisoflavan-4-ol4′,5,7-Triacetoxyisoflavan-4-ol 4′,7,8-Trihydroxyisoflavan-4-ol7,8-Dihydroxy-4-methoxyisoflavan-4-ol4′,7-Dihydroxy-8-methylisoflavan-4-ol3′,7-Dihydroxy-8-methylisoflavan-4-ol7-Hydroxy-4′-methoxy-8-methylisoflavan-4-ol 4′,7-Dihydroxy-3′-methoxy-8-methylisoflavan-4-ol 4′,5,7-Trihydroxyisoflavan-4-ol
 46. Acompound of formula III selected from the group consisting of:4′,7,8-Triacetoxydehydroequol (4′,7,8-Triaceioxyisoflav-3-ene) 7,8-Diacetoxy-4-methoxydehydroequol (7,8-Diacetoxy-4-methoxyisoflav-3-ene)4′,7-Diacetoxy-g-methylisoflav-3 -ene3′,7-Diacetoxy-8-methylisoflav-3-ene7-Acetoxy-4′-methoxy-8-methylisoflav-3-ene4′,7-Diacetoxy-3′-methoxy-8-methylisoflav-3-ene4′,5,7-Triacetoxyisoflav-3-ene Isoflav-3-ene-4′,7,8-triol4′-Methoxyisoflav-3-ene-7,8-diol 8-Methylisoflav-3-ene-4′,7-diol8-Methylisoflav-3-ene-3′,7-diol 4′-Methoxy-8-methylisoflav-3 -ene-7-ol3′-Methoxy-8-methylisoflav-3 -ene-4′,7-diol Isoflav-3-ene-4′,5,7-triol